Filed Pursuant to Rule 424(b)(2)

Registration Statement No. 333-220576

CALCULATION OF REGISTRATION FEE

PROSPECTUS SUPPLEMENT

(To Prospectus dated September 22, 2017)

8,500,000 Shares

Common Stock

We expect to enter into a forward sale agreement with each of Bank of America, N.A. and Citibank, N.A., which we refer to in this capacity as the forward purchasers. In connection with the forward sale agreements, the forward purchasers or their affiliates are borrowing from third parties and selling to the underwriters an aggregate of 8,500,000 shares of our common stock (or an aggregate of 9,775,000 shares of our common stock if the underwriters’ option to purchase additional shares is exercised in full) that will be delivered in this offering.

We will not initially receive any proceeds from the sale of shares of our common stock by the forward purchasers or their affiliates. We expect to physically settle the forward sale agreements (by the delivery of shares of our common stock) and receive proceeds from the sale of those shares of our common stock upon one or more forward settlement dates no later than September 27, 2019. We may also elect to cash settle or net share settle all or a portion of our obligations under a forward sale agreement if we conclude it is in our best interest to do so. If we elect to cash settle a forward sale agreement, we may not receive any proceeds and we may owe cash to the relevant forward purchaser in certain circumstances. If we elect to net share settle a forward sale agreement, we will not receive any proceeds, and we may owe shares of our common stock to the relevant forward purchaser in certain circumstances. See “Underwriting (Conflicts of Interest)—Forward Sale Agreements.”

If any forward purchaser or its affiliates does not sell on the anticipated closing date of this offering all of the shares of our common stock to be sold by it to the underwriters, we will issue and sell to the underwriters a number of shares of our common stock equal to the number of shares of our common stock that the forward purchaser or its affiliate does not sell and the number of shares underlying the relevant forward sale agreement will be decreased in respect of the number of shares that we issue and sell.

We are organized and conduct our operations to qualify as a real estate investment trust, or REIT, for U.S. federal income tax purposes. To assist us in complying with certain federal income tax requirements applicable to REITs, our charter contains certain restrictions relating to the ownership and transfer of our stock, including an ownership limit of 9.8% (by value or by number of shares, whichever is more restrictive) on the outstanding shares of our common stock.

Our common stock is listed on the New York Stock Exchange under the symbol “DLR”. The last reported sale price of our common stock on the New York Stock Exchange on September 24, 2018 was $115.92 per share.

Investing in our common stock involves risks. See “Risk Factors” beginning on page S-23 of this prospectus supplement.

Neither the U.S. Securities and Exchange Commission (the “SEC”) nor any state securities commission or other regulatory body has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

The forward purchasers have granted the underwriters a 30-day option from the date of this prospectus supplement, exercisable in whole or in part from time to time, to purchase up to an additional 1,275,000 shares of our common stock at the initial price to the public less the underwriting discount. Upon any exercise of such option, the number of shares of our common stock underlying each forward sale agreement will be increased by the number of shares sold by the applicable forward purchaser or its affiliate in respect of such option exercise. In such event, if any forward purchaser or its affiliates does not deliver and sell all of the shares of our common stock to be sold by it in connection with the exercise of such option, we will issue and sell to the underwriters a number of shares of our common stock equal to the number of shares that the forward purchaser or its affiliates does not deliver and sell, and the number of shares underlying the relevant forward sale agreement will not be increased in respect of the number of shares that we issue and sell.

The underwriters expect to deliver the shares to purchasers on or about September 27, 2018 through the book-entry facilities of The Depository Trust Company.

Joint Book-Running Managers

Wells Fargo Securities

Senior Co-Manager

SunTrust Robinson Humphrey

Co-Managers

September 24, 2018

You should rely only on the information contained or incorporated by reference in this prospectus supplement, the accompanying prospectus and any “free writing prospectus” we authorize to be delivered to you. We have not, and the underwriters and the forward purchasers (and their affiliates) have not, authorized anyone else to provide you with different or additional information. If anyone provides you with different or additional information you should not rely on it. We are not, and the underwriters and the forward purchasers (and their affiliates) are not, making an offer of these securities or soliciting an offer to buy these securities in any jurisdiction where the offer is not permitted. You should assume that the information appearing in this prospectus supplement and the accompanying prospectus, including the documents incorporated by reference herein and therein, and any authorized “free writing prospectus” is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates. The descriptions set forth in this prospectus supplement replace and supplement, where inconsistent, the description of the general terms and provisions set forth in the accompanying prospectus.

TABLE OF CONTENTS

Prospectus Supplement

Prospectus

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the terms of the offering of the shares and also adds to and updates information contained in the accompanying prospectus as well as the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. The second part, the accompanying prospectus, gives more general information about securities we may offer from time to time, some of which does not apply to the shares we are offering. To the extent any inconsistency or conflict exists between the information included in this prospectus supplement and the information included in the accompanying prospectus, the information included or incorporated by reference in this prospectus supplement updates and supersedes the information in the accompanying prospectus. This prospectus supplement incorporates by reference important business and financial information about us that is not included in or delivered with this prospectus supplement.

It is important for you to read and consider all information contained in this prospectus supplement and the accompanying prospectus in making your investment decision. You should also read and consider the information contained in the documents identified under the heading “Where You Can Find More Information.”

Unless otherwise indicated or unless the context requires otherwise, all references in this prospectus supplement and the accompanying prospectus to “we,” “us,” “our,” “the company,” “our company” or “Digital Realty” refer to Digital Realty Trust, Inc. together with our consolidated subsidiaries, including Digital Realty Trust, L.P., a Maryland limited partnership, of which Digital Realty Trust, Inc. is the sole general partner and which we refer to in this prospectus supplement and the accompanying prospectus as “the operating partnership” or “our operating partnership”.

All references in this prospectus supplement to our operating partnership’s global revolving credit facility mean our operating partnership’s $2.0 billion senior unsecured revolving credit facility and global senior credit agreement, and all references in this prospectus supplement to our operating partnership’s term loan facility mean our operating partnership’s senior unsecured multi-currency term loan facility and term loan agreement, which governs a $1.25 billion five-year senior unsecured term loan and a $300 million seven-year senior unsecured term loan.

“Turn-Key Flex^®,” “Powered Base Buildings^®,” “POD Architecture^®” and “Critical Facilities Management^®” are trademarks of our company. All other trademarks or trade names appearing in this prospectus supplement and the accompanying prospectus are the property of their respective owners.

The distribution of this prospectus supplement, the accompanying prospectus, any authorized “free writing prospectus” and the offering of the shares may be restricted by law. If you possess this prospectus supplement, the accompanying prospectus or any authorized “free writing prospectus,” you should find out about and observe these restrictions. This prospectus supplement, the accompanying prospectus and any authorized “free writing prospectus” are not an offer to sell the shares and are not soliciting an offer to buy the shares in any jurisdiction where the offer or sale is not permitted or where the person making the offer or sale is not qualified to do so or to any person to whom it is not permitted to make such offer or sale. See “Underwriting (Conflicts of Interest)” in this prospectus supplement.

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RISK FACTORS

In addition to other information contained or incorporated by reference in this prospectus supplement, the accompanying prospectus and any “free writing prospectus” we authorize to be delivered to you, you should carefully consider the risks described below and incorporated herein by reference to our Combined Annual Report on Form 10-K for the year ended December 31, 2017, and other subsequent filings of Digital Realty Trust, Inc. and Digital Realty Trust, L.P. under the Securities Exchange Act of 1934, as amended, or the Exchange Act, in evaluating our company, our properties and our business before making a decision to invest in our common stock. These risks are not the only ones faced by us. Additional risks not presently known to us or that we currently deem immaterial could also materially and adversely affect our financial condition, results of operations, business and prospects. The trading price of our common stock could decline due to any of these risks, and you may lose all or part of your investment. This prospectus supplement, the accompanying prospectus and the documents incorporated herein and therein by reference also contain forward-looking statements that involve risks and uncertainties. Actual results could differ materially from those anticipated in these forward-looking statements as a result of certain factors, including the risks faced by us described below and elsewhere in this prospectus supplement, the accompanying prospectus and the documents incorporated herein and therein by reference. Please refer to the section below entitled “Forward-Looking Statements.”

Risks Related to the Proposed Ascenty Acquisition

We cannot assure you that the proposed Ascenty acquisition will be completed on a timely basis or at all.

There are a number of risks and uncertainties relating to the Ascenty acquisition. For example, the Ascenty acquisition may not be completed, or may not be completed in the time frame, on the terms or in the manner currently anticipated, as a result of a number of factors, including the failure of the parties to satisfy one or more of the conditions to closing. There can be no assurance that the conditions to closing of the Ascenty acquisition will be satisfied or waived or that other events will not intervene to delay or result in the failure to close the Ascenty acquisition. The definitive agreements related to the Ascenty acquisition may be terminated by the parties thereto under certain circumstances. In addition, certain properties may not be acquired, or may be acquired on different terms, if certain conditions are not satisfied or if certain regulatory approvals are not obtained.

In addition, our operating partnership has agreed to guarantee the obligations of Acquisition Sub under the definitive agreements related to the Ascenty acquisition. In the event that Acquisition Sub is unable to complete the Ascenty acquisition due to a failure of Acquisition Sub to perform or otherwise, Ascenty may enforce our operating partnership’s guarantee and require our operating partnership to complete the Ascenty acquisition. Delays in closing the Ascenty acquisition or the failure of Acquisition Sub to close the Ascenty acquisition in its entirety or at all may result in our incurring significant additional costs in connection with such delay or failure and/or failing to achieve the anticipated benefits of the Ascenty acquisition. Any delay in closing or a failure of Acquisition Sub to close the Ascenty acquisition could have a negative impact on our business and the trading price of our common stock.

In the event the Ascenty acquisition is not consummated and we elect to physically settle the forward sale agreements, we may use the proceeds from such settlement(s) for general corporate purposes, including, but not limited to, the repayment of outstanding indebtedness, the repurchase, redemption or retirement of outstanding debt or preferred equity securities, and the funding of development and acquisition opportunities. However, we would have broad authority to use such net proceeds for other purposes that may not be accretive to our earnings per share and funds from operations per share. Affiliates of certain of the underwriters are lenders under our global revolving credit facility and would receive a pro rata portion of the net proceeds from the physical settlement of the forward sale agreements to the extent that we use any such proceeds to reduce the outstanding balance under such facility. See “Underwriting (Conflicts of Interest).”

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If completed, the Ascenty acquisition may not achieve its intended benefits or may disrupt our plans and operations.

There can be no assurance that we will be able to realize the expected benefits of the Ascenty acquisition, which may result in material unanticipated problems, including:

Many of these risks will be outside of our control and any one of them could result in increased costs, decreases in the amount of expected revenue, disruptions in our current plans and operations and diversion of our management’s time and energy, which could have a material adverse effect on our business, financial condition, results of operations and/or cash flows. In addition, we may not realize the full benefits of the Ascenty acquisition within the anticipated time frame or at all. All of these factors could cause dilution to our earnings per share, decrease or delay the expected accretive effect of the Ascenty acquisition, and/or negatively impact the price of our common stock.

We may suffer economic harm as a result of making unsuccessful acquisitions in a new region and expanding our business in emerging economies, such as Brazil, elsewhere in Latin America or other economically volatile areas.

The Ascenty portfolio is located in a region where we have not previously owned properties or conducted any operations. This acquisition may entail risks in addition to those we face in other acquisitions where we are familiar with the regions, such as the risk that we do not complete development or expansions on time or on budget or correctly anticipate conditions or trends in a new region and are therefore not able to operate the acquired properties profitably. If this occurs, it could adversely affect our financial position, results of operations, cash flows and ability to make expected distributions to our stockholders.

In addition, we are contemplating further expansion in South America through the JV Entity, elsewhere in Latin America and in other emerging economies, which tend to have more volatile economies and governments than those in many of the countries in which we currently operate. The risk of doing business in emerging economies, such as Brazil, elsewhere in Latin America or other economically volatile areas, could adversely affect our operations and earnings. Such risks include the financial instability among customers in these regions,

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political instability, fraud or corruption and other non-economic factors such as irregular trade flows that need to be managed successfully with the help of the local governments. In addition, commercial laws in some emerging economies can be vague, inconsistently administered and retroactively applied. If we are deemed not to be in compliance with applicable laws in emerging economies where we conduct business, our prospects and business in those countries could be harmed, which could then have a material adverse impact on our results of operations and financial position. Our failure to successfully manage economic, political and other risks relating to doing business in emerging economies and economically and politically volatile areas could adversely affect our business.

The Brazilian government has exercised, and continues to exercise, significant influence over the Brazilian economy. This influence, as well as Brazilian political and economic conditions, could adversely affect us.

Ascenty’s portfolio of data centers is concentrated in Brazil. The Brazilian government frequently intervenes in the Brazilian economy and occasionally makes significant changes in policy and regulations. The Brazilian government’s actions designed to control inflation, stimulate growth and other policies and regulations have often involved, among other measures, increases in interest rates, changes in tax policies, price controls, currency devaluations, capital controls and limits on imported goods and services. We cannot control or predict changes in policy or regulations that the Brazilian government might adopt in the future.

We may be adversely affected by the economic and political conditions in Brazil as well as changes in policy or regulations at the federal, state or municipal levels involving or affecting factors such as:

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The actual stabilized EBITDA for Ascenty may not be consistent with the estimated stabilized EBITDA used to estimate the purchase price multiple set forth in this prospectus supplement.

As a part of our underwriting of the Ascenty acquisition and business due diligence process, we developed an estimate of the annualized stabilized EBITDA for Ascenty. The stabilized EBITDA estimate is comprised of (i) our estimate of annualized run-rate EBITDA for Ascenty based on Ascenty’s EBITDA for the month ended July 31, 2018, which is the most recently completed full month for which Ascenty provided us with financial information as part of our underwriting and due diligence process, (ii) our forward estimate of the stabilized EBITDA contribution from signed leases with respect to approximately 12.6 megawatts and additional colocation space leases at Ascenty’s in-service data centers that have been signed as of the date of this prospectus supplement but had not yet commenced as of July 31, 2018 and leases pending execution that are subject to closing or other conditions under the Share Purchase Agreement, (iii) our forward estimate of the stabilized EBITDA contribution from leases with respect to approximately 18.0 megawatts of additional capacity expected to be built at Ascenty’s data centers under construction that have been signed as of the date of this prospectus supplement but had not yet commenced as of July 31, 2018 and leases pending execution that are subject to closing or other conditions under the Share Purchase Agreement, (iv) our forward estimate of the stabilized EBITDA contribution from the potential lease-up of approximately 38.6 megawatts of additional capacity expected to be built at Ascenty’s under-construction data centers as of the date of this prospectus supplement, and (v) our forward estimate of the stabilized EBITDA contribution from fiber leases that have been signed as of the date of this prospectus supplement but had not yet commenced as of July 31, 2018. We have assumed that the EBITDA margins for signed but not yet commenced leases, leases pending execution that are subject to closing or other conditions under the Share Purchase Agreement and future leases of additional capacity to be built at both the in-service and under-construction data centers will be consistent with the EBITDA margins of existing in-service data centers once they have been fully leased. In addition, in underwriting our estimate of stabilized EBITDA, we have straight-lined existing contractual rents and estimated future rents in accordance with GAAP.

We caution you not to place undue reliance on our underwriting or our estimate of the stabilized EBITDA or the resulting estimated purchase price multiple because it is based solely on data made available to us in the diligence process in connection with the Ascenty acquisition and includes a number of assumptions, including the timely and on-budget completion of all space to be constructed, the timely leasing of all additional capacity, certain assumptions regarding currency exchange rates and the absence of customer defaults or early lease terminations. Furthermore, the estimated stabilized EBITDA is not calculated in accordance with GAAP and includes estimates of future rents and operating expenses based on our expectations for Ascenty going forward. Our experience operating Ascenty may change our expectations with respect to the estimated stabilized EBITDA. In addition, the actual stabilized EBITDA for Ascenty may differ from our expectations based on numerous other factors, including potential difficulties encountered in connection with the construction and lease-up of additional data center space, currency fluctuations, unanticipated incremental general and administrative expenses or operating expenses, the results of our final purchase price allocation, difficulties in leasing incremental capacity or collecting anticipated revenue, customer bankruptcies and unanticipated expenses at the data centers that we cannot pass on to customers, as well as the risk factors set forth in this prospectus supplement and the accompanying prospectus and documents incorporated by reference herein and therein. The construction and lease-up of the additional capacity included in the assumptions underlying our estimate of stabilized EBITDA may not be completed within the timeframe or on the terms we have assumed, or at all. We can provide no assurance that the actual stabilized EBITDA for Ascenty will be consistent with the estimated stabilized EBITDA used to estimate the purchase price multiple set forth in this prospectus supplement.

In addition, our estimate of stabilized EBITDA for Ascenty is not calculated in the same manner in which we calculate EBITDA or Adjusted EBITDA with respect to our company in this prospectus supplement or other documents that we may make available to investors on our website or otherwise or furnish in Current Reports on Form 8-K filed with the SEC from time to time. As a result, stabilized EBITDA for Ascenty may not be a useful tool for investors to evaluate or compare Ascenty’s EBITDA to our company’s EBITDA or Adjusted EBITDA,

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particularly because our estimate of stabilized EBITDA for Ascenty is based on several assumptions that are described above.

All of Ascenty’s facilities are held through leasehold interests and the rights with respect to such properties will be significantly less than if such properties where held though fee interests.

Ascenty does not own any of its facilities, but instead operates its business as a lessee through leasehold interests. The current weighted average remaining lease term for all of its facilities is over 30 years, assuming the exercise of extension options. Upon expiration, Ascenty may be unable to renew these leases on favorable terms, or at all, which could adversely affect our ability to realize the anticipated benefits of the Ascenty acquisition. If Ascenty is not able to renew the leases at any of the leased Ascenty properties, the costs of relocating the equipment in such data centers and developing a new location into a high-quality data center could be prohibitive. Ascenty could lose customers due to the disruptions in their operations caused by any relocation. Ascenty could also lose those customers that choose its data centers based primarily on their locations.

The landlords of the leased properties may have certain contractual or statutory rights that limit Ascenty’s use of the leased properties or operational flexibility with respect to such properties, including the ability to develop, expand or otherwise modify such properties. The exercise of such rights could result in termination of the leases. In addition, certain of the leasehold interests are subordinated to senior debt such as mortgages, which, if Ascenty fails to obtain a non-disturbance agreement or tenant easement, could foreclose on Ascenty’s real property interests if the underlying property owner defaults on the mortgage and, as a result, the lease could be terminated. There can be no assurance that Ascenty will be able to obtain non-disturbance agreements or tenant easements from the lenders of the third-party landlords.

We may be subject to unknown or contingent liabilities related to the Ascenty properties for which we may have no or limited recourse against the sellers.

The Ascenty properties may be subject to unknown or contingent liabilities for which we may have no or limited recourse against the sellers. Unknown or contingent liabilities might include liabilities for clean-up or remediation of environmental conditions, claims of customers, vendors or other persons dealing with the acquired entities, tax liabilities and other liabilities whether incurred in the ordinary course of business or otherwise. The purchase agreement pursuant to which Acquisition Sub agreed to acquire Ascenty contains certain representations and warranties from the sellers; however, the sellers’ obligation to indemnify us for breaches of the representations and warranties contained in the purchase agreement is limited to claims of intentional acts or omissions constituting fraud. In connection with the Ascenty acquisition, we intend to obtain a representation and warranty insurance policy, but we cannot make a claim under this policy for a breach of a non-fundamental representation, as identified in the policy, after the date that is three years after the date of closing of the acquisition or a breach of a fundamental representation or certain tax obligations after the date that is six years after the date of the closing of the acquisition. Accordingly, if any issues arise post-closing, there can be no assurance that we will recover any amounts with respect to losses due to breaches of the sellers’ representations and warranties. In addition, the total amount of costs and expenses that we may incur with respect to liabilities associated with Ascenty properties may exceed our expectations, which may adversely affect our business, financial condition and results of operations.

If the Ascenty acquisition is not completed, we will have incurred substantial expenses without our stockholders realizing the expected benefits.

If we are unable to complete the Ascenty acquisition, we will have incurred significant due diligence, legal, accounting and other transaction costs in connection with the Ascenty acquisition and potential joint venture without our stockholders realizing the anticipated benefits. We cannot assure you that we will acquire Ascenty because the proposed Ascenty acquisition is subject to a variety of factors, including the satisfaction of customary closing conditions.

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Development and construction of the Ascenty development properties and expansions of the Ascenty in-service properties may not be completed as anticipated, or at all, and development and expansion activities may cost more and take longer than we estimate.

The construction of development properties or expansions of in-service properties are complex projects that require us to acquire and allocate resources in such a manner that may adversely impact our ability to successfully pursue other projects, or to construct and complete such projects on time and within budget.

Development and construction involves many risks, including:

Our reporting currency is the U.S. dollar, but revenue, costs and expenses associated with Ascenty will be denominated in the Brazilian real, so that exchange rate movements may affect our financial performance.

Ascenty will generate a portion of its revenue, and incur costs and expenses, in Brazilian reais. These operations will translate into U.S. dollars when we prepare our consolidated financial statements. As a result, a significant decrease or volatility in the value of the Brazilian real could materially affect our revenues and results of operations. During the past few decades, the Brazilian currency in particular has faced frequent and substantial exchange rate fluctuations in relation to foreign currencies mostly because of political and economic conditions. There can be no assurance that the Brazilian real will not significantly appreciate or depreciate against the U.S. dollar in the future. We also bear the risk that the rate of inflation in the foreign countries where we incur costs and expenses or the decline in value of the U.S. dollar compared to those foreign currencies will increase our costs as expressed in U.S. dollars. For example, future measures by the Central Bank of Brazil to control inflation, including interest rate adjustments, intervention in the foreign exchange market and actions to fix the value of the Brazilian real, may weaken the U.S. dollar in Brazil. Whether in Brazil or elsewhere, we may not be able to adjust the prices of our products to offset the effects of inflation or foreign currency appreciation on our cost structure, which could increase our costs and reduce our net operating margins. If we do not successfully manage these risks through various mechanisms, our revenues and results of operations could be adversely affected.

Our business could be harmed if certain of Ascenty’s key management personnel terminate their relationship with us.

Ascenty’s success depends, to a significant extent, on the continued services of Christopher P. Torto, Ascenty’s current chief executive officer, and other members of Ascenty’s senior management team. Mr. Torto

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has agreed to enter into a new management agreement to be effective upon completion of the Ascenty acquisition. Notwithstanding this agreement, there can be no assurance that Mr. Torto or the other members of Ascenty’s senior management team will continue to provide services to Ascenty. The loss of services of one or more members of Ascenty’s senior management team could harm our business and our prospects.

Risks Related to the Proposed Joint Venture

We cannot assure you that Brookfield will complete its committed investment in the JV Entity prior to the completion of the Ascenty acquisition or at all.

We have entered into a bilateral equity commitment letter with Brookfield, pursuant to which Brookfield has committed to acquire an interest equal to ours in a joint venture entity that is expected to ultimately own Ascenty in an amount equal to the sum of (i) up to $725.0 million in respect of the equity portion of the purchase price for the Ascenty acquisition, plus (ii) an amount equal to 50% of any additional amounts up to a specified cap that we contribute to the joint venture entity after closing of the Ascenty acquisition but prior to Brookfield’s investment in the joint venture entity, plus (iii) an amount equal to 50% of our and Brookfield’s aggregate transaction expenses in connection with the Ascenty acquisition (which transaction expenses will be reimbursed by the joint venture entity to the applicable party). To the extent that their investment occurs after the closing of the Ascenty acquisition, Brookfield has also committed to pay interest on their committed amount at a rate of 8% for the first 90 days after the closing of the Ascenty acquisition and increasing to 10% thereafter until such time as their investment in the joint venture is made. However, there can be no assurance that Brookfield will complete its committed investment in the JV Entity prior to the completion of the Ascenty acquisition, on the terms currently anticipated, or at all. The Ascenty acquisition is not contingent upon completion of Brookfield’s investment in the JV Entity, and we will still be obligated to complete the Ascenty acquisition in the event Brookfield fails to invest in the JV Entity prior to the Ascenty acquisition or at all. If Brookfield does not complete its investment in the JV Entity, we may be forced to bear the entire expense of the Ascenty acquisition indefinitely and the relative size of our investment in Ascenty will be twice as large as it would have otherwise been. As a result, we would be exposed to a much greater degree to the various risks related to the Ascenty acquisition described in this prospectus supplement. If Brookfield’s investment in the JV Entity occurs after the consummation of the Ascenty acquisition, we anticipate funding the portion of the equity to be provided by Brookfield with a $750.0 million short-term senior unsecured term loan, which may result in our incurring significant additional costs. Any delay by, or failure of, Brookfield to invest in the JV Entity could have a negative impact on our business and the trading price of our common stock.

Our joint ventures, including the JV Entity, could be adversely affected by our lack of decision-making authority, our reliance on joint venture partner’s financial condition and disputes between us and our joint venture partner.

We have entered into a bilateral equity commitment letter with Brookfield to invest in the JV Entity, and we may invest in additional joint ventures in the future. Investments in joint ventures may, under certain circumstances, involve risks not present when a third party is not involved, including reliance on our joint venture partner and the possibility that our joint venture partner might become bankrupt, engage in malfeasance or fail to fund their share of required capital contributions, thus exposing us to liabilities in excess of our share of the investment. Joint ventures generally provide for a reduced level of control over an acquired project because governance rights are shared with others. For example, should Brookfield invest in the JV Entity, we anticipate initially owning only 50% of the voting equity interests in the JV Entity, and that certain major decisions relating to the business of the JV Entity and Ascenty will require the affirmative vote of directors or equityholders representing at least 75% of the voting equity interests in the JV Entity. Accordingly, certain major decisions involving the business of the JV Entity and Ascenty, including the approval of any amendments to the JV Entity’s governing documents, the approval of business plans and annual budgets, appointment or dismissal of the chief executive officer or chief financial officer, related party transactions, material acquisitions and divestitures, any fundamental change in the business of the JV Entity and Ascenty, expansion into new countries,

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financings and winding up or dissolution of the JV Entity, will require the affirmative vote of directors or equityholders representing at least 75% of the voting equity interests in the JV Entity; provided, that so long as (i) our operating partnership (together with certain affiliates) owns 20% of the voting equity interests in the JV Entity, the approval of our operating partnership shall also be required for any matter otherwise requiring such super-majority approval; and (ii) Brookfield (together with certain affiliates) owns 20% of the voting equity interests in the JV Entity, the approval of Brookfield shall also be required for any matter otherwise requiring such super-majority approval. Brookfield may have business interests or goals that are inconsistent with our business interests or goals, and might take actions contrary to our policies or objectives. Such investments, including our investment in the JV Entity, may also have the potential risk of deadlock or impasses on significant decisions, such as a sale of the business, significant investments or capital expenditures, or capital raising, because neither we nor our joint venture partner would have full control over the joint venture. Any disputes that may arise between us and our joint venture partner may result in litigation or arbitration that could increase our expenses and may prevent our officers and/or directors from focusing their time and effort on our business. Consequently, actions by, or disputes with, our joint venture partner might result in subjecting properties owned by the joint venture to additional risk. In addition, we may in certain circumstances be liable for the actions of our joint venture partner.

It may be difficult for us to exit the JV Entity after an impasse with Brookfield.

In our joint venture with Brookfield, there may be a potential risk of impasse or deadlock in some joint venture decisions because our approval and the approval of other joint venture partners may be required for significant decisions. In particular, certain major decisions relating to the business of the JV Entity, including the approval of business plans and annual budgets, appointment or dismissal of the chief executive officer or chief financial officer, related party transactions, material acquisitions and divestitures, expansion into new countries, financings and winding up or dissolution of the JV Entity, require the affirmative vote of directors or equityholders representing at least 75% of the voting equity interests in the JV Entity.

In addition, in the event of a dispute between the equityholders, it may be difficult for an equityholder to leave the joint venture. We expect that transfers of voting equity interests in the JV Entity, other than to affiliates, will be prohibited until the fifth anniversary of the closing of the Ascenty acquisition. After the fifth anniversary, equityholders are expected to be able to transfer their voting equity interests in the JV Entity, subject to the other equityholders’ right of first offer to purchase such voting equity interests. In addition, if an equityholder transfers equity interests in the JV Entity representing at least 10% of the total equity interests in the JV Entity, then the remaining equityholders are expected to have tag-along rights to participate in such sale. At any time after the fifth anniversary of the closing of the Ascenty acquisition, an equityholder holding more than 40% of the JV Entity’s total voting equity interests is expected to have the right to unilaterally force the JV Entity to conduct an initial public offering (either of itself or a subsidiary), subject to the other voting equityholders’ right to purchase the triggering equityholder’s interest in the JV Entity. At any time after the seventh anniversary of the closing of the Ascenty acquisition, an equityholder holding more than 40% of the JV Entity’s total voting equity interests is expected to have the right to unilaterally force the JV Entity to commence a sale process for the sale of the company, subject to the other voting equityholders’ right of first offer to purchase the triggering equityholder’s interest in the JV Entity (with such seven-year holding period reduced to five years upon the occurrence of certain limited deadlock events). In the event that one equityholder wishes to transfer its voting equity interests, it is possible that neither party will have the funds necessary to complete a buy-out as described above. In addition, we may experience difficulty in locating a third-party purchaser for our joint venture interest and in obtaining a favorable sale price for the interest. As a result, it is possible that we may not be able to exit the relationship if an impasse develops.

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Risks Related to this Offering

Our cash available for distribution to stockholders may not be sufficient to make distributions at expected levels, and we may need to borrow in order to make such distributions; consequently, we may not be able to make such distributions in full.

If cash available for distribution generated by our assets is less than our estimate or if such cash available for distribution decreases in future periods from expected levels, our inability to make the expected distributions could result in a decrease in the market price of our common stock.

Distributions made by us will be authorized and determined by our board of directors in its sole discretion out of funds legally available therefor and will be dependent upon a number of factors, including restrictions under applicable law and our capital requirements. We may not be able to make or sustain distributions in the future. Distributions we make out of our current or accumulated earnings and profits will be treated as dividends for U.S. federal income tax purposes. To the extent that we decide to make distributions in excess of our current and accumulated earnings and profits, such distributions would generally be considered a return of capital for U.S. federal income tax purposes to the extent of the holder’s adjusted tax basis in its shares. A return of capital is not taxable, but it has the effect of reducing the holder’s adjusted tax basis in its investment. To the extent that distributions exceed the adjusted tax basis of a holder’s shares, they will be treated as a gain from the sale or exchange of such stock. See “United States Federal Income Tax Considerations—Taxation of Taxable U.S. Holders of Our Capital Stock” in our Current Report on Form 8-K filed on June 14, 2018. If we borrow to fund distributions, our future interest costs would increase, thereby reducing our earnings and cash available for distribution from what they otherwise would have been.

We have significant outstanding indebtedness that involves significant debt service obligations, limits our operational and financial flexibility, exposes us to interest rate fluctuations and exposes us to the risk of default under our debt obligations.

As of June 30, 2018, after giving pro forma effect to this offering and the use of proceeds therefrom, and assuming that the Brookfield investment in the JV Entity is completed concurrently with the closing of the Ascenty acquisition, we would have had a total combined indebtedness, including capital lease obligations, of approximately $9.3 billion (excluding approximately $281.8 million of Brazilian operating company level secured term loan indebtedness that is not consolidated). There are no limits on the amount of indebtedness we may incur other than limits contained in our existing debt financing agreements or future agreements that we may enter into or as may be set forth in any policy limiting the amount of indebtedness we may incur adopted by our board of directors. A substantial level of indebtedness could have adverse consequences for our business, financial condition and results of operations because it could, among other things:

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Market interest rates and other factors may affect the value of our common stock.

One of the factors that will influence the price of our common stock will be the dividend yield on our common stock relative to market interest rates. Increases in market interest rates could cause the market price of our common stock to decrease. The market price of the shares of our common stock will also depend on many other factors, which may change from time to time, including:

In addition, over the last several years, prices of equity securities in the U.S. trading markets have been experiencing extreme price fluctuations, and the market prices of our common stock have also fluctuated significantly during this period. As a result of these and other factors, investors who purchase our common stock in this offering may experience a decrease, which could be substantial and rapid, in the market price of our common stock, including decreases unrelated to our operating performance or prospects.

Our global revolving credit facility and term loan facility may limit our ability to pay distributions to our common stockholders.

Our global revolving credit facility and our term loan facility prohibit us from making distributions to our stockholders, or redeeming or otherwise repurchasing shares of our capital stock, including our common stock, after the occurrence and during the continuance of an event of default, except in limited circumstances including as necessary to enable us to maintain our qualification as a REIT and to avoid the payment of income or excise tax. Consequently, after the occurrence and during the continuance of an event of default under our global revolving credit facility or term loan facility, we may not be able to pay all or a portion of the dividends payable to the holders of our common stock.

In addition, in the event of a default under our global revolving credit facility or term loan facility, we would be unable to borrow under such facilities and any amounts that we have borrowed thereunder could become immediately due and payable. The agreements governing our future debt instruments may also include restrictions on our ability to pay dividends to holders of our common stock.

The number of shares available for future sale could adversely affect the market price of our common stock.

We cannot predict whether future issuances of shares of our common stock or the availability of shares for resale in the open market will decrease the market price per share of our common stock. Sales of a substantial number of shares of our common stock in the public market, the issuance of substantial additional shares or the perception that such sales or issuances might occur could materially adversely affect the market price of the

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shares of our common stock. In addition, future issuances of shares of our common stock may be dilutive to existing stockholders. Some of the potential share issuances that may adversely affect the market price of the shares of our common stock could include: the exercise of the underwriters’ option to purchase additional shares, the exchange of our operating partnership’s units for our common stock, the granting, exercise or vesting of any options, restricted stock or restricted stock units or long-term incentive units in our operating partnership granted to certain directors, executive officers and other employees under our incentive award plans, the issuance of our common stock upon conversion of our outstanding preferred stock (in connection with specified change of control transactions), the issuance of our common stock or our operating partnership’s units in connection with property, portfolio or business acquisitions and other issuances of our common stock, our securities exchangeable for or convertible into our common stock, our operating partnership’s units or our operating partnership’s securities exchangeable for or convertible into our common stock.

We have granted those persons who received units in the formation transactions related to our initial public offering certain registration rights with respect to the shares of our common stock for which their units may be redeemed or exchanged pursuant to the partnership agreement of our operating partnership. These registration rights required us to file a “shelf” registration statement covering all such shares of common stock. A shelf registration statement and a related prospectus supplement covering these shares have been filed and are currently effective.

Our executive officers have agreed with the underwriters not to offer, sell, contract to sell, pledge or otherwise dispose of any shares of common stock or other securities convertible or exchangeable into our common stock for a period of 45 days after the date of this prospectus supplement. If any or all of these holders cause a large number of their shares to be sold in the public market, the sales could reduce the trading price of our common stock and could impede our ability to raise future capital.

For a discussion of potential dilution resulting from the forward sale agreements, see “—Risks Related to the Forward Sale Agreements—Provisions in the forward sale agreements could result in substantial dilution to our earnings per share and return on equity or result in substantial cash payment obligations.”

The market price and trading volume of our common stock may be volatile.

The market price of our common stock may be volatile. In addition, the trading volume in our common stock may fluctuate and cause significant price variations to occur. If the market price of our common stock declines significantly, you may be unable to resell your shares at or above the public offering price. We cannot assure you that the market price of our common stock will not fluctuate or decline significantly in the future.

Some of the factors that could negatively affect the market price of our common stock or result in fluctuations in the market price or trading volume of our common stock include:

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Future offerings of debt, which would be senior to our common stock upon liquidation, and/or preferred equity securities, which may be senior to our common stock for purposes of distributions or upon liquidation, may adversely affect the market price of our common stock.

In the future, we may attempt to increase our capital resources by making offerings of debt or preferred equity securities, including medium-term notes, exchangeable notes, trust preferred securities, senior or subordinated notes and preferred stock, and entering into new loan agreements. Upon liquidation, holders of our debt securities and shares of preferred stock and lenders with respect to other borrowings will receive distributions of our available assets prior to the holders of our common stock. Additional equity and equity-linked offerings may dilute the holdings of our existing stockholders or reduce the market price of our common stock, or both. Holders of our common stock are not entitled to preemptive rights or other protections against dilution. Holders of our series C cumulative redeemable perpetual preferred stock, series G cumulative redeemable preferred stock, series H cumulative redeemable preferred stock, series I cumulative redeemable preferred stock and series J cumulative redeemable preferred stock have a preference on liquidating distributions and a preference on dividend payments that could limit our ability to pay a dividend or make another distribution to the holders of our common stock. Because our decision to issue securities in any future offering and to enter into new loan agreements will depend on market conditions and other factors, many of which are beyond our control, we cannot predict or estimate the amount, timing or nature of our future offerings or borrowings. Thus, our stockholders bear the risk of our future offerings or loan arrangements reducing the market price of our common stock, reducing our assets available to them upon our liquidation and diluting their stock holdings in us.

Our earnings and cash distributions will affect the market price of shares of our common stock.

To the extent that the market value of a REIT’s equity securities is based primarily upon market perception of the REIT’s growth potential and its current and potential future cash distributions, whether from operations, sales, acquisitions, development or refinancing and is secondarily based upon the value of the underlying assets, shares of our common stock may trade at prices that are higher or lower than the net asset value per share. To the extent we retain operating cash flow for investment purposes, working capital reserves or other purposes rather than distributing the cash flow to stockholders, these retained funds, while increasing the value of our underlying assets, may negatively impact the market price of our common stock. Our failure to meet market expectations with regard to future earnings and cash distributions would likely adversely affect the market price of our common stock.

Risks Related to the Forward Sale Agreements

Provisions in the forward sale agreements could result in substantial dilution to our earnings per share and return on equity or result in substantial cash payment obligations.

If any forward purchaser or its affiliate does not sell all the shares of our common stock to be sold by it pursuant to the terms of the underwriting agreement (including because insufficient shares of our common stock were made available by securities lenders for borrowing at a stock loan cost below a specified threshold), we will issue and sell directly to the underwriters the number of shares of our common stock not sold by the relevant forward purchaser or its affiliate and, under such circumstances, the number of shares of our common stock underlying the relevant forward sale agreement will be decreased by the number of shares of our common stock that we issue and sell. The stock loan market is volatile, and it is uncertain whether sufficient shares of our common stock will be made available prior to closing.

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Each forward purchaser will have the right to accelerate its forward sale agreement (with respect to all or any portion of the transaction under such forward sale agreement that the forward purchaser determines is affected by an event described below) and require us to settle on a date specified by such forward purchaser if:

A forward purchaser’s decision to exercise its right to accelerate the settlement of any forward sale agreement will be made irrespective of our interests, including our need for capital. In such cases, we could be required to issue and deliver shares of our common stock under the physical settlement provisions of the applicable forward sale agreement irrespective of our capital needs, which would result in dilution to our earnings per share and return on equity.

We expect that the forward sale agreements will settle no later than September 27, 2019. However, a forward sale agreement may be settled earlier in whole or in part at our option. Subject to certain conditions, we generally have the right to elect physical, cash or net share settlement under each forward sale agreement. A forward sale agreement will be physically settled by delivery of shares of our common stock, unless we elect to cash settle or net share settle such forward sale agreement. Delivery of shares of our common stock upon physical settlement (or, if we elect net share settlement, upon such settlement to the extent we are obligated to deliver shares of our common stock) will result in dilution to our earnings per share and return on equity. If we elect cash settlement or net share settlement with respect to all or a portion of the shares of our common stock underlying a forward sale agreement, we expect the applicable forward purchaser (or an affiliate thereof) to purchase a number of shares of our common stock in secondary market transactions over an unwind period to:

In addition, the purchase of shares of our common stock in connection with a forward purchaser or its affiliate unwinding its hedge positions could cause the price of shares of our common stock to increase over such time (or prevent a decrease over such time), thereby increasing the amount of cash we would owe to such forward purchaser (or decreasing the amount of cash that the forward purchaser would owe us) upon a cash settlement of the relevant forward sale agreement or increasing the number of shares of our common stock we

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would deliver to such forward purchaser (or decreasing the number of shares of our common stock that such forward purchaser would deliver to us) upon net share settlement of the relevant forward sale agreement.

The forward sale price that we expect to receive upon physical settlement of a forward sale agreement will be subject to adjustment on a daily basis based on a floating interest rate factor equal to a specified daily rate less a spread and will be decreased based on amounts related to expected dividends on our common stock during the term of the applicable forward sale agreement. If the specified daily rate is less than the spread on any day, the interest factor will result in a daily reduction of the forward sale price. As of the filing of this prospectus supplement, the specified daily rate was greater than the spread. If the weighted average price at which a forward purchaser (or its affiliate) is able to purchase shares during the applicable unwind period under a forward sale agreement is above the relevant forward sale price, in the case of cash settlement, we would pay the applicable forward purchaser under such forward sale agreement an amount in cash equal to the difference or, in the case of net share settlement, we would deliver to such forward purchaser a number of shares of our common stock having a value equal to the difference. Thus, we could be responsible for a potentially substantial cash payment in the case of cash settlement. If the weighted average price at which a forward purchaser (or its affiliate) is able to purchase shares during the applicable unwind period under a forward sale agreement is below the relevant forward sale price, in the case of cash settlement, we would be paid the difference in cash by the relevant forward purchaser under such forward sale agreement or, in the case of net share settlement, we would receive from such forward purchaser a number of shares of our common stock having a value equal to the difference. See “Underwriting (Conflicts of Interest)—Forward Sale Agreements” for information on the forward sale agreements.

In case of our bankruptcy or insolvency, the forward sale agreements would automatically terminate, and we would not receive the expected proceeds from the sale of shares of our common stock.

If we or a regulatory authority with jurisdiction over us institutes, or we consent to, a proceeding seeking a judgment in bankruptcy or insolvency or any other relief under any bankruptcy or insolvency law or other similar law affecting creditors’ rights, or we or a regulatory authority with jurisdiction over us presents a petition for our winding-up or liquidation, or we consent to such a petition, the forward sale agreements will automatically terminate. If a forward sale agreement so terminates, we would not be obligated to deliver to the applicable forward purchaser any shares of our common stock not previously delivered, and such forward purchaser would be discharged from its obligation to pay the relevant forward sale price per share in respect of any shares of our common stock not previously settled. Therefore, to the extent that there are any shares of our common stock with respect to which such forward sale agreement has not been settled at the time of the commencement of any such bankruptcy or insolvency proceedings, we would not receive the relevant forward sale price per share in respect of those shares of our common stock.

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FORWARD-LOOKING STATEMENTS

We make statements in this prospectus supplement, the accompanying prospectus and the documents incorporated herein and therein by reference that are forward-looking statements within the meaning of the federal securities laws. In particular, statements pertaining to the Ascenty acquisition and related financings, the proposed joint venture with Brookfield, our capital resources, expected physical settlement of the forward sale agreements and use of proceeds from any such settlement, expected use of borrowings under our credit facility, portfolio performance, our ability to lease vacant space and space under development, leverage policy, acquisition and capital expenditure plans, capital recycling program, returns on invested capital, supply and demand for data center space, capitalization rates, expected proceeds from assets sales and cash flows from operations, rents to be received in future periods and expected rental rates on new or renewed data center space contain forward-looking statements. Likewise, all of our statements regarding anticipated market conditions, demographics and results of operations are forward-looking statements. You can identify forward-looking statements by the use of forward-looking terminology such as “believes,” “expects,” “may,” “will,” “should,” “seeks,” “approximately,” “intends,” “plans,” “pro forma,” “estimates” or “anticipates” or the negative of these words and phrases or similar words or phrases which are predictions of or indicate future events or trends and discussions which do not relate solely to historical matters. You can also identify forward-looking statements by discussions of strategy, plans or intentions.

Forward-looking statements involve numerous risks and uncertainties and you should not rely on them as predictions of future events. Forward-looking statements depend on assumptions, data or methods that may be incorrect or imprecise and that we may not be able to realize. We do not guarantee that the transactions and events described will happen as described or that they will happen at all. The following factors, among others, could cause actual results and future events to differ materially from those set forth or contemplated in the forward-looking statements:

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While forward-looking statements reflect our good faith beliefs, they are not guarantees of future performance. We disclaim any obligation to publicly update or revise any forward-looking statement to reflect changes in underlying assumptions or factors, new information, data or methods, future events or other changes. The risks included here are not exhaustive, and additional factors could adversely affect our business and financial performance, including factors and risks included in other sections of this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein or therein. Those risks continue to be relevant to our performance and financial condition. Moreover, we operate in a very competitive and rapidly changing environment. New risk factors emerge from time to time and it is not possible for management to predict all such risk factors, nor can we assess the impact of all such risk factors on our business or the extent to

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which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements. Given these risks and uncertainties, investors should not place undue reliance on forward-looking statements as a prediction of actual results. For a further discussion of these and other factors that could impact our future results, performance or transactions, see the section entitled “Risk Factors” in this prospectus supplement, in the accompanying prospectus and in our Combined Annual Report on Form 10-K for the year ended December 31, 2017, as may be updated by subsequent filings with the SEC that are incorporated by reference herein and therein.

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USE OF PROCEEDS

We will not initially receive any proceeds from the sale of shares of our common stock by the forward purchasers or their affiliates. We expect to physically settle the forward sale agreements (by the delivery of shares of our common stock) and receive proceeds from the sale of those shares of our common stock upon one or more forward settlement dates no later than September 27, 2019. We may also elect to cash settle or net share settle all or a portion of our obligations under a forward sale agreement if we conclude it is in our best interest to do so. If we elect to cash settle a forward sale agreement, we may not receive any proceeds and we may owe cash to the relevant forward purchaser in certain circumstances. If we elect to net share settle a forward sale agreement, we will not receive any proceeds, and we may owe shares of our common stock to the relevant forward purchaser in certain circumstances. See “Underwriting (Conflicts of Interest)—Forward Sale Agreements.”

Assuming full physical settlement of the forward sale agreements at an initial forward sale price of $109.045 per share, we expect to receive net proceeds of approximately $928.1 million (or $1,067.5 million if the underwriters’ option to purchase additional shares is exercised in full) (in each case after deducting the underwriting discounts and fees and estimated expenses related to the forward sale agreements and this offering), subject to certain adjustments pursuant to the forward sale agreements, upon settlement of the forward sale agreements, which settlement we expect will occur no later than September 27, 2019. The forward sale price that we expect to receive upon physical settlement of a forward sale agreement will be subject to adjustment on a daily basis based on a floating interest rate factor equal to a specified daily rate less a spread and will be decreased based on amounts related to expected dividends on shares of our common stock during the term of the applicable forward sale agreement. If the specified daily rate is less than the spread on any day, the interest factor will result in a daily reduction of the forward sale price. As of the filing of this prospectus supplement, the specified daily rate was greater than the spread.

We intend to contribute the net proceeds, if any, received upon the settlement of the forward sale agreements (and from the sale of any shares of common stock sold by us to the underwriters in connection with this offering) to our operating partnership, which intends to subsequently use a portion of such net proceeds to fund its portion of the JV Entity’s acquisition of Ascenty, including transaction expenses. Our operating partnership intends to use the balance of such net proceeds, if any, to repay borrowings outstanding under its global revolving credit facility and for general corporate purposes, including, the repayment of other outstanding indebtedness, the repurchase, redemption or retirement of outstanding debt or preferred equity securities, future capital contributions to the joint venture and the funding of development and acquisition opportunities.

If, however, we elect to cash settle the forward sale agreements, we would expect to receive an amount of net proceeds that is significantly lower than the estimate included under this caption, and we may not receive any net proceeds (or may owe cash to the forward purchasers). If we elect to net share settle the forward sale agreements in full, we would not receive any proceeds from the forward purchasers.

Before the issuance of shares of our common stock, if any, upon settlement of the forward sale agreements, the forward sale agreements will be reflected in our diluted earnings per share calculations using the treasury stock method. Under this method, the number of shares of our common stock used in calculating diluted earnings per share is deemed to be increased by the excess, if any, of the number of shares of common stock that would be issued upon full physical settlement of the forward sale agreements over the number of shares of common stock that could be purchased by us in the market (based on the average market price during the period) using the proceeds receivable upon full physical settlement (based on the adjusted forward sale price at the end of the reporting period).

In the event the Ascenty acquisition is not consummated and we elect to physically settle the forward sale agreements, we may use the proceeds from such settlement(s) (and from the sale of any shares of common stock sold by us to the underwriters in connection with this offering), if any, for general corporate purposes, including,

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but not limited to, the repayment of outstanding indebtedness, the repurchase, redemption or retirement of outstanding debt or preferred equity securities, and the funding of development and acquisition opportunities.

Our operating partnership’s global revolving credit facility provides for borrowings in Australian dollars, British pound sterling, Canadian dollars, Euros, Hong Kong dollars, Japanese yen, Singapore dollars, and U.S. dollars, and includes the ability to add additional currencies in the future, subject to the receipt of lender commitments in such currencies and the satisfaction of other conditions. As of June 30, 2018, our operating partnership’s global revolving credit facility had a total outstanding balance of $472.4 million, excluding committed letters of credit of $22.8 million, leaving approximately $1.5 billion available for use. As of June 30, 2018, borrowings under operating partnership’s global revolving credit facility bore interest at an overall blended rate of 2.21% comprised of 3.09% (U.S. dollars), 0.63% (Euro), 2.94% (Australian dollars), 2.88% (Hong Kong dollars), 0.92% (Japanese yen), 2.42% (Singapore dollars and 2.64% (Canadian dollars). The interest rates are based on 1-month LIBOR, 1-month EURIBOR, 1-month BBR, 1-month HIBOR, 1-month JPY LIBOR, 1-month SOR and 1- month CDOR, respectively, plus a margin of 1.00%, and U.S. Prime Rate. We have used and intend to use borrowings under our operating partnership’s global revolving credit facility to acquire additional properties or businesses, fund development opportunities and to provide for working capital and other corporate purposes, including potentially for the repurchase, redemption or retirement of outstanding debt or equity securities.

Certain of the underwriters are joint lead arrangers and bookrunners, and affiliates of certain of the underwriters are lenders, syndication agents, issuing banks, swing line banks and an administrative agent under our global revolving credit facility and would receive a pro rata portion of the net proceeds from the physical settlement of the forward sale agreements (and from the sale of any shares of common stock sold by us to the underwriters), if any, to the extent that we use any such proceeds to reduce the outstanding balance under such facility. See “Underwriting (Conflicts of Interest).”

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CAPITALIZATION

The following table sets forth Digital Realty Trust, Inc.’s cash and cash equivalents and capitalization as of June 30, 2018.

The following table does not give effect to the Ascenty acquisition or the proposed joint venture with Brookfield.

This information should be read in conjunction with, and is qualified in its entirety by, Digital Realty Trust, Inc.’s consolidated financial statements and schedule and the notes to its financial statements included in our Combined Quarterly Report on Form 10-Q for the three months ended June 30, 2018 and our Combined Annual Report on Form 10-K for the year ended December 31, 2017, each of which is incorporated by reference in this prospectus supplement and the accompanying prospectus.

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SUPPLEMENTAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

For a discussion of certain material United States federal income tax consequences regarding our company and holders of our common stock, please see Exhibit 99.1 to our Current Report on Form 8-K filed with the SEC on June 14, 2018, which was filed pursuant to Item 8.01 of Form 8-K. Such Form 8-K (including Exhibit 99.1 thereto) is incorporated by reference into the accompanying prospectus and supersedes and replaces, in its entirety, the discussion under the heading “United States Federal Income Tax Considerations” in the accompanying prospectus and in our registration statement on Form S-3 (File Nos. 333-220576) filed with the SEC on September 22, 2017. Prospective investors in our common stock should consult their tax advisors regarding the United States federal income and other tax considerations to them of the acquisition, ownership and disposition of our common stock offered by this prospectus supplement.

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UNDERWRITING (CONFLICTS OF INTEREST)

Merrill Lynch, Pierce, Fenner & Smith Incorporated and Citigroup Global Markets Inc. are acting as the representatives of the underwriters named below. Subject to the terms and conditions stated in the underwriting agreement, dated the date of this prospectus supplement, each underwriter named below has severally agreed to purchase, and the forward purchasers, or their affiliates, have agreed to sell the number of shares set forth opposite the underwriter’s name.

The underwriters are offering the shares of common stock subject to their acceptance of the shares of common stock from the forward purchasers, or their affiliates, or, in certain circumstances described herein, us, and subject to prior sale. The underwriting agreement provides that the obligations of the underwriters to pay for and accept delivery of the shares included in this offering are subject to approval of certain legal matters by counsel and to certain other conditions. The underwriters are obligated to take and pay for all the shares of common stock offered by this prospectus supplement if any such shares are taken, other than those covered by the option described below.

The shares of common stock sold by the underwriters to the public will initially be offered at the initial public offering price set forth on the cover of this prospectus supplement. After the initial offering of the shares of common stock, the underwriters may change the public offering price and the other selling terms. The offering of the shares of common stock by the underwriters is subject to receipt and acceptance and subject to the underwriters’ right to reject any order in whole or in part.

We and our operating partnership have agreed that, for a period of 45 days from the date of this prospectus supplement, we and it will not offer, sell, contract to sell, pledge or otherwise dispose of (or enter into a transaction which is designed to, or would reasonably be expected to, have the same effect), directly or indirectly, including the filing (or participation in the filing) with the SEC of a registration statement under the

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Securities Act of 1933, as amended, or the Securities Act, relating to, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Exchange Act with respect to, any shares of any class of our common stock (other than the shares offered hereby), limited partnership units of our operating partnership, or securities convertible into or exercisable or exchangeable for any of the foregoing, or publicly announce an intention to make any such offer, sale, pledge, disposition or filing, without the prior written consent of Merrill Lynch, Pierce, Fenner & Smith Incorporated and Citigroup Global Markets Inc. except that we may:

Our executive officers have agreed, subject to certain limited exceptions (including an exception for any transaction consummated in accordance with a valid contract, instruction or plan that satisfies the requirements of Rule 10b5-1 under the Exchange Act), that, for a period of 45 days from the date of this prospectus supplement, they will not offer, sell, contract to sell, pledge or otherwise dispose of (or enter into a transaction which is designed to, or would reasonably be expected to, have the same effect), directly or indirectly, including the filing (or participation in the filing) with the SEC of a registration statement or make any demand for or exercise any registration right in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Exchange Act with respect to, any class of our common stock or limited partnership units of our operating partnership, or securities convertible into or exercisable or exchangeable for any of the foregoing, enter into any swap, hedge or other arrangement that transfers, in whole or in part, any of the economic consequences of ownership of any of the foregoing, whether any of these transactions are to be settled by delivery of shares of our capital stock or other securities, or publicly announce an intention to make any offer, sale, pledge or disposition, or to enter into any transaction, swap, hedge or other arrangement, without, in each case, the prior written consent of Merrill Lynch, Pierce, Fenner & Smith Incorporated and Citigroup Global Markets Inc.

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The shares are listed on the New York Stock Exchange under the symbol “DLR”.

The following table shows the underwriting discounts and commissions that we are to pay to the underwriters in connection with this offering.

The information assumes (a) either no exercise or full exercise of the underwriters’ option to purchase additional shares, and (b) that the forward sale agreements are fully physically settled based upon the initial forward sale price of $109.045 per share. If we physically settle the forward sale agreements based upon the initial forward sale price, we expect to receive net proceeds of approximately $928.1 million (or $1,067.5 million if the underwriters’ option to purchase additional shares is exercised in full) (after deducting the underwriting discounts and fees and estimated expenses related to the forward sale agreement and this offering), subject to certain adjustments as described below, upon settlement of the forward sale agreements, which settlement we expect will occur no later than September 27, 2019.

We estimate that our portion of the total expenses related to the forward sale agreements and this offering will be approximately $1.2 million.

The underwriters have agreed to reimburse us in an amount up to $2,761,437.50.

In connection with the offering, the underwriters may purchase and sell shares of our common stock in the open market. Purchases and sales in the open market may include short sales, purchases to cover short positions, which may include purchases pursuant to the underwriters’ option to purchase additional shares, and stabilizing purchases.

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Purchases to cover short positions and stabilizing purchases, as well as other purchases by the underwriters for their own accounts, may have the effect of preventing or retarding a decline in the market price of the shares. They may also cause the price of the shares to be higher than the price that would otherwise exist in the open market in the absence of these transactions. The underwriters may conduct these transactions on the New York Stock Exchange, in the over-the-counter market or otherwise. If the underwriters commence any of these transactions, they may discontinue them at any time.

Forward Sale Agreements

We have entered into separate forward sale agreements with each of Bank of America, N.A. and Citibank, N.A., which we refer to in this capacity as the forward purchasers, relating to an aggregate of 8,500,000 shares of our common stock (subject to increase if the underwriters exercise their option to purchase additional shares). In connection with the execution of the forward sale agreements, the forward purchasers or their affiliates are borrowing from third parties and selling to the underwriters in this offering an aggregate of up to 8,500,000 shares of our common stock (subject to increase if the underwriters exercise their option to purchase additional shares). If any forward purchaser or its affiliate does not sell all the shares of our common stock to be sold by it to the underwriters pursuant to the terms of the underwriting agreement, we will issue and sell directly to the underwriters the number of shares of our common stock not sold by the relevant forward purchaser or its affiliate and, under such circumstances, the number of shares of our common stock underlying the relevant forward sale agreement will be decreased by the number of shares of our common stock that we issue and sell. Under any such circumstance, the commitment of the underwriters to purchase shares of our common stock from the relevant forward purchaser or its affiliate, as described above, will be replaced with the commitment to purchase from us, at the price set forth on the cover page of this prospectus supplement at which the underwriters have agreed to purchase the shares of our common stock from such forward purchaser, the relevant number of shares of our common stock not sold by such forward purchaser or its affiliate.

We will not initially receive any proceeds from the sale of our common stock by the forward purchasers or their affiliates, but we expect to receive an amount equal to the net proceeds from the sale of the borrowed shares of our common stock sold in this offering, subject to certain adjustments pursuant to the forward sale agreements, at the applicable forward sale price (as described below), from the forward purchasers upon full physical settlement of the forward sale agreements. We will only receive such proceeds if we elect to fully physically settle the forward sale agreements.

We expect each forward sale agreement to settle no later than September 27, 2019, subject to acceleration by the relevant forward purchaser upon the occurrence of certain events. On a settlement date, if we decide to physically settle any forward sale agreement, we will issue shares of our common stock to the forward purchaser under the relevant forward sale agreement at the then-applicable forward sale price. The forward sale price initially will be equal to the public offering price to public less the underwriting discount per share, as set forth on the cover page of this prospectus supplement. Each of the forward sale agreements provides that the forward sale price will be subject to adjustment on a daily basis based on a floating interest rate factor equal to a specified daily rate less a spread and will be decreased by amounts related to expected dividends on our common stock during the term of such forward sale agreement. If the specified daily rate is less than the spread on any day, the interest factor will result in a daily reduction of the forward sale price. As of the filing of this prospectus supplement, the specified daily rate was greater than the spread.

Before settlement of any forward sale agreement, we expect that the shares issuable upon settlement of such forward sale agreement will be reflected in our diluted earnings per share, return on equity and dividends per share calculations using the treasury stock method. Under this method, the number of shares of our common stock used in calculating diluted earnings per share, return on equity and dividends per share is deemed to be increased by the excess, if any, of the number of shares of our common stock that would be issued upon full physical settlement of such forward sale agreement over the number of shares of our common stock that could be purchased by us in the market (based on the average market price during the period) using the proceeds receivable upon full physical settlement (based on the adjusted forward sale price at the end of the reporting period). Consequently, we anticipate there will be no dilutive effect on our earnings per share prior to physical or

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net share settlement of the forward sale agreements and subject to the occurrence of certain events, except during periods when the average market price of our common stock is above the applicable forward sale price, which is initially $109.045 per share (equal to the initial price to the public less the underwriting discount per share, as set forth on the cover page of this prospectus supplement), subject to adjustment based on a floating interest rate factor equal to a specified daily rate less a spread, and subject to decrease by amounts related to expected dividends on our common stock during the term of the forward sale agreements. However, if we decide to physically or net share settle any forward sale agreement, delivery of our shares on any physical settlement or net share settlement of such forward sale agreement will result in dilution to our earnings per share, return on equity and dividends per share.

Except under limited circumstances described below and subject to certain conditions, we have the right to elect physical, cash or net share settlement under any forward sale agreement. A forward sale agreement will be physically settled by delivery of shares of our common stock, unless we elect to cash settle or net share settle such forward sale agreement. Delivery of shares of our common stock upon physical settlement (or, if we elect net share settlement, upon such settlement to the extent we are obligated to deliver shares of our common stock) will result in dilution to our earnings per share and return on equity. If we elect cash settlement or net share settlement with respect to all or a portion of the shares of our common stock underlying a forward sale agreement, we expect the applicable forward purchaser (or an affiliate thereof) to purchase a number of shares of our common stock in secondary market transactions over an unwind period to:

If the weighted average price at which a forward purchaser (or its affiliate) is able to purchase shares during the applicable unwind period under a forward sale agreement is above the relevant forward sale price, in the case of cash settlement, we would pay the applicable forward purchaser under such forward sale agreement an amount in cash equal to the difference or, in the case of net share settlement, we would deliver to such forward purchaser a number of shares of our common stock having a value equal to the difference. Thus, we could be responsible for a potentially substantial cash payment in the case of cash settlement. If the weighted average price at which a forward purchaser (or its affiliate) is able to purchase shares during the applicable unwind period under a forward sale agreement is below the relevant forward sale price, in the case of cash settlement, we would be paid the difference in cash by the relevant forward purchaser under such forward sale agreement or, in the case of net share settlement, we would receive from such forward purchaser a number of shares of our common stock having a value equal to the difference.

In addition, the purchase of shares of our common stock in connection with the relevant forward purchaser or its affiliate unwinding its hedge positions could cause the price of our common stock to increase over time (or prevent a decrease over such time), thereby increasing the amount of cash we would owe to the forward purchaser (or decreasing the amount of cash that the forward purchaser would owe us) upon a cash settlement of the relevant forward sale agreement or increasing the number of shares of our common stock we would deliver to such forward purchaser (or decreasing the number of shares of our common stock that such forward purchaser would deliver to us) upon net share settlement of the relevant forward sale agreement. See “Risk Factors—Risks Related to the Forward Sale Agreements.”

Each forward purchaser will have the right to accelerate its forward sale agreement (with respect to all or any portion of the transaction under such forward sale agreement that the relevant forward purchaser determines is affected by such event) and require us to settle on a date specified by such forward purchaser if (1) in such forward purchaser’s commercially reasonable judgment, it or its affiliate (x) is unable to hedge in a commercially reasonable manner its exposure under such forward sale agreement because insufficient shares of our common stock have been made available for borrowing by securities lenders or (y) would incur a stock loan cost in excess of a specified threshold to hedge in a commercially reasonable manner its exposure under such forward sale

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agreement; (2) we declare any dividend, issue or distribution on shares of our common stock (a) payable in cash in excess of specified amounts, (b) that constitutes an extraordinary dividend under the forward sale agreement, (c) payable in securities of another company as a result of a spin-off or similar transaction, or (d) of any other type of securities (other than our common stock), rights, warrants or other assets for payment at less than the prevailing market price; (3) certain ownership thresholds applicable to such forward purchaser and its affiliates are exceeded; (4) an event is announced that if consummated would result in a specified extraordinary event (including certain mergers or tender offers, as well as certain events involving our nationalization or insolvency or a delisting of our common stock) or the occurrence of a change in law or disruption in the forward purchaser’s ability to hedge its exposure under the forward sale agreement; or (5) certain other events of default or termination events occur, including, among others, any material misrepresentation made in connection with such forward sale agreement or our insolvency (each as more fully described in each forward sale agreement). A forward purchaser’s decision to exercise its right to accelerate any forward sale agreement and to require us to settle any such forward sale agreement will be made irrespective of our interests, including our need for capital. In such cases, we could be required to issue and deliver shares of our common stock under the terms of the physical settlement provisions of the applicable forward sale agreement irrespective of our capital needs, which would result in dilution to our earnings per share and return on equity. In addition, upon certain events of bankruptcy, insolvency or reorganization relating to us, the forward sale agreement will terminate without further liability of either party. Following any such termination, we would not issue any shares of our common stock and we would not receive any proceeds pursuant to the forward sale agreement. See “Risk Factors—Risks Related to the Forward Sale Agreements.”

Option to Purchase Additional Shares

The forward purchasers have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus supplement, to purchase up to 1,275,000 additional shares at the initial price to the public less the underwriting discount. If the underwriters exercise this option, each underwriter will be obligated, subject to the conditions contained in the underwriting agreement, to purchase a number of additional shares approximately proportionate to that underwriter’s initial allocation reflected in the above table. Upon any exercise of such option, the number of shares of our common stock underlying each forward sale agreement will be increased by the number of shares sold by the applicable forward purchaser or its affiliate to the underwriters in respect of such option exercise. In such event, if any forward purchaser or its affiliates does not deliver and sell all of the shares of our common stock to be sold by it in connection with the exercise of such option, we will issue and sell to the underwriters a number of shares of our common stock equal to the number of shares that the forward purchaser or its affiliate does not deliver and sell and the number of shares underlying the relevant forward sale agreement will not be increased in respect of the number of shares that we issue and sell.

Conflicts of Interest

All of the proceeds of this offering (excluding proceeds paid to us with respect to any shares of our common stock that we may sell to the underwriters in lieu of the forward purchasers or their affiliates selling our common stock to the underwriters) will be paid to the forward purchasers. As a result, affiliates of Merrill Lynch, Pierce, Fenner & Smith Incorporated and Citigroup Global Markets Inc. will receive more than 5% of the net proceeds of this offering, not including the underwriting discount.

In the ordinary course of their business, the underwriters, the forward purchasers, or their respective affiliates have in the past performed, and may continue to perform, investment banking, broker dealer, financial advisory or other services for us, for which they received or may receive, customary fees and commissions.

In connection with the Ascenty acquisition, Citigroup Global Markets Inc. has agreed to provide the committed facilities described elsewhere in this prospectus supplement. In addition, affiliates of Merrill Lynch, Pierce, Fenner & Smith Incorporated, Citigroup Global Markets Inc., J.P. Morgan Securities LLC, SMBC Nikko Securities America, Inc., Scotia Capital (USA) Inc., TD Securities (USA) LLC, Barclays Capital Inc., Credit Suisse Securities (USA) LLC, Deutsche Bank Securities Inc., MUFG Securities Americas Inc., Mizuho

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Securities USA LLC, Morgan Stanley & Co. LLC, PNC Capital Markets LLC, RBC Capital Markets, LLC, Wells Fargo Securities, LLC, SunTrust Robinson Humphrey, Inc., and BB&T Capital Markets, a division of BB&T Securities, LLC are lenders, affiliates of SMBC Nikko Securities America, Inc., Scotia Capital (USA) Inc., TD Securities (USA) LLC, Barclays Capital Inc., Credit Suisse Securities (USA) LLC, Deutsche Bank Securities Inc., MUFG Securities Americas Inc., Morgan Stanley & Co. LLC, and Wells Fargo Securities, LLC are co-documentation agents, affiliates of Mizuho Securities USA LLC, PNC Capital Markets LLC and SunTrust Robinson Humphrey, Inc. are senior managing agents, affiliates of RBC Capital Markets, LLC and BB&T Capital Markets, a division of BB&T Securities, LLC are managing agents, an affiliate of Citigroup Global Markets Inc. is the administrative agent, affiliates of Merrill Lynch, Pierce, Fenner & Smith Incorporated and J.P. Morgan Securities LLC are syndication agents, Merrill Lynch, Pierce, Fenner & Smith Incorporated, Citigroup Global Markets Inc. and J.P. Morgan Securities LLC are joint lead arrangers and joint book running managers, affiliates of Merrill Lynch, Pierce, Fenner & Smith Incorporated, Citigroup Global Markets Inc. and J.P. Morgan Securities LLC are issuing banks and affiliates of Citigroup Global Markets Inc. are swing line banks under our operating partnership’s global revolving credit facility. Therefore, such underwriters and/or affiliates of such underwriters may receive more than 5% of the net proceeds from this offering through the repayment of the borrowings under the global revolving credit facility.

An affiliate of Citigroup Global Markets Inc. is the administrative agent, affiliates of Merrill Lynch, Pierce, Fenner & Smith Incorporated and J.P. Morgan Securities LLC are syndication agents, affiliates of SMBC Nikko Securities America, Inc., Scotia Capital (USA) Inc., TD Securities (USA) LLC, Barclays Capital Inc., Credit Suisse Securities (USA) LLC, MUFG Securities Americas Inc., Morgan Stanley & Co. LLC and Wells Fargo Securities, LLC are co-documentation agents, affiliates of Mizuho Securities USA LLC, PNC Capital Markets LLC and SunTrust Robinson Humphrey, Inc. are senior managing agents, affiliates of Raymond James & Associates, Inc. and BB&T Capital Markets, a division of BB&T Securities, LLC are managing agents, Merrill Lynch, Pierce, Fenner & Smith Incorporated, Citigroup Global Markets Inc., J.P. Morgan Securities LLC, TD Securities (USA) LLC and affiliates of SMBC Nikko Securities America, Inc. and Scotia Capital (USA) Inc. are joint lead arrangers and joint book running managers, and affiliates of Merrill Lynch, Pierce, Fenner & Smith Incorporated, Citigroup Global Markets Inc., J.P. Morgan Securities LLC, SMBC Nikko Securities America, Inc., Scotia Capital (USA) Inc., TD Securities (USA) LLC, Barclays Capital Inc., Credit Suisse Securities (USA) LLC, MUFG Securities Americas Inc., Mizuho Securities USA LLC, PNC Capital Markets LLC, Wells Fargo Securities, LLC, SunTrust Robinson Humphrey, Inc., Raymond James & Associates, Inc. and BB&T Capital Markets, a division of BB&T Securities, LLC are lenders under our term loan facility.

Affiliates of Wells Fargo Securities, LLC are trustees under our 3.400% notes due 2020, our 3.625% notes due 2022, our 3.950% notes due 2022, our 4.750% notes due 2025, our 2.750% notes due 2023, our 3.700% notes due 2027, and our 4.450% notes due 2028. Affiliates of Deutsche Bank Securities Inc. are trustees under our 5.250% notes due 2021, our 4.250% notes due 2025, our 4.750% notes due 2023, our 2.750% notes due 2024, our 3.300% notes due 2029, our 2.625% notes due 2024 and our floating rate notes due 2019. Merrill Lynch, Pierce, Fenner & Smith Incorporated, Citigroup Global Markets Inc., Credit Suisse Securities (USA) LLC, Deutsche Bank Securities Inc. and Morgan Stanley & Co. LLC are also sales agents under our equity distribution agreements, pursuant to which we can issue and sell shares of our common stock having an aggregate offering price of up to $400.0 million from time to time through them.

In addition, certain of the underwriters, the forward purchasers, or their respective affiliates in the past have leased, currently lease and in the future may lease space from us.

We have agreed to indemnify the several underwriters and the several forward purchasers against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters or the several forward purchasers, as applicable, may be required to make because of any of those liabilities.

In connection with the offering, certain of the underwriters or securities dealers may distribute prospectuses by electronic means, such as email.

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Notice to Prospective Investors in Australia

No placement document, prospectus, product disclosure statement or other disclosure document has been lodged with the Australian Securities and Investments Commission (“ASIC”), in relation to this offering. This prospectus supplement does not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the “Corporations Act”), and does not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

Any offer in Australia of the shares may only be made to persons (the “Exempt Investors”) who are “sophisticated investors” (within the meaning of section 708(8) of the Corporations Act), “professional investors” (within the meaning of section 708(11) of the Corporations Act) or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the shares without disclosure to investors under Chapter 6D of the Corporations Act.

The shares applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under this offering, except in circumstances where disclosure to investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring the shares must observe such Australian on-sale restrictions.

This prospectus supplement contains general information only and does not take account of the investment objectives, financial situation or particular needs of any particular person. It does not contain any securities recommendations or financial product advice. Before making an investment decision, investors need to consider whether the information in this prospectus supplement is appropriate to their needs, objectives and circumstances, and, if necessary, seek expert advice on those matters.

Notice to Prospective Investors in Canada

The shares may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the shares must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 (or, in the case of securities issued or guaranteed by the government of a non-Canadian jurisdiction, section 3A.4) of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Notice to Prospective Investors in the Dubai International Financial Centre

This prospectus supplement relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority (“DFSA”). This prospectus supplement is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection

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with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for this prospectus supplement. The shares to which this prospectus supplement relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the shares offered should conduct their own due diligence on the shares. If you do not understand the contents of this prospectus supplement you should consult an authorized financial advisor.

Notice to Prospective Investors in Hong Kong

The shares have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the shares has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to the shares which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance and any rules made under that Ordinance.

Notice to Prospective Investors in the United Kingdom

In addition, in the United Kingdom, this document is being distributed only to, and is directed only at, and any offer subsequently made may only be directed at persons who are “qualified investors” (as defined in the Prospectus Directive) (i) who have professional experience in matters relating to investments falling within Article 19 (5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the “Order”) and/or (ii) who are high net worth companies (or persons to whom it may otherwise be lawfully communicated) falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”). This document must not be acted on or relied on in the United Kingdom by persons who are not relevant persons. In the United Kingdom, any investment or investment activity to which this document relates is only available to, and will be engaged in with, relevant persons.

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LEGAL MATTERS

Certain legal matters will be passed upon for us by Latham & Watkins LLP, Los Angeles, California and for the underwriters by Goodwin Procter LLP, Boston, Massachusetts and Cleary Gottlieb Steen & Hamilton LLP, New York, New York. Venable LLP, Baltimore, Maryland, will issue an opinion to us regarding certain matters of Maryland law, including the validity of the common stock offered hereby.

EXPERTS

The consolidated financial statements and financial statement schedule III of Digital Realty Trust, Inc. and its subsidiaries as of December 31, 2017 and 2016 and for each of the years in the three-year period ended December 31, 2017 and management’s assessment of the effectiveness of internal control over financial reporting as of December 31, 2017 have all been incorporated by reference in this prospectus supplement in reliance upon the reports of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

The consolidated financial statements and financial statement schedule III of Digital Realty Trust, L.P. and its subsidiaries as of December 31, 2017 and 2016 and for each of the years in the three-year period ended December 31, 2017 have all been incorporated by reference in this prospectus supplement in reliance upon the report of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

The audited historical financial statements of DuPont Fabros Technology, Inc. and DuPont Fabros Technology, L.P. included in Digital Realty Trust, Inc.’s and Digital Realty Trust, L.P.’s Current Reports on Form 8-K filed on July 10, 2017 and August 2, 2017, have been so incorporated in reliance on the report of Ernst & Young LLP, independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any document we file with the SEC at the SEC’s public reference rooms at 100 F Street, N.E. Room 1580, Washington, DC 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference rooms. The SEC also maintains a web site that contains reports, proxy and information statements, and other information regarding registrants that file electronically with the SEC at www.sec.gov. You can inspect reports and other information we file at the offices of the NYSE, 20 Broad Street, New York, New York 10005. In addition, we maintain a web site that contains information about us at www.digitalrealty.com. The information found on, or otherwise accessible through, our website is not incorporated into, and does not form a part of, this prospectus supplement, the accompanying prospectus or any other report or document we file with or furnish to the SEC.

We have filed with the SEC a registration statement on Form S-3 (File Nos. 333-220576), of which this prospectus supplement and the accompanying prospectus are a part, including exhibits, schedules and amendments filed with, or incorporated by reference in, such registration statement, under the Securities Act. This prospectus supplement and the accompanying prospectus do not contain all of the information set forth in the registration statement and exhibits and schedules to the registration statement. For further information with respect to our company, reference is made to the registration statement, including the exhibits to the registration statement. Statements contained in this prospectus supplement and the accompanying prospectus as to the contents of any contract or other document referred to, or incorporated by reference, in this prospectus supplement and the accompanying prospectus are not necessarily complete and, where that contract or document

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is an exhibit to the registration statement, each statement is qualified in all respects by the exhibit to which the reference relates. Copies of the registration statement, including the exhibits and schedules to the registration statement, may be examined at the SEC’s public reference rooms at 100 F Street, N.E. Room 1580, Washington, DC 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference rooms. Copies of all or a portion of the registration statement can be obtained from the public reference rooms of the SEC upon payment of prescribed fees. The registration statement is also available to you on the SEC’s web site at www.sec.gov.

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INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE