FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person *   Kaiser Maile 2. Date of Event Requiring Statement (Month/Day/Year) 07/26/2018 3. Issuer Name and Ticker or Trading Symbol CoreSite Realty Corp [COR] (Last) (First) (Middle) C/O CORESITE REALTY CORPORATION, 1001 17TH STREET, SUITE 500 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Senior Vice President, Sales 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) DENVER, CO 80202 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock 10,172 (1) D Â

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Kaiser Maile C/O CORESITE REALTY CORPORATION 1001 17TH STREET, SUITE 500 DENVER, CO 80202	Â	Â	  Senior Vice President, Sales	Â

Signatures

/s/ Derek S. McCandless, Attorney-in-Fact		07/30/2018
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Includes 8,387 shares of unvested restricted stock awards granted to the reporting person under the issuer's 2010 Equity Incentive Award Plan. The unvested shares of restricted stock vest as follows: (i) 777 shares vest on March 3, 2019, (ii) 922 shares vest in two equal annual installments on October 1, 2018 and October 1, 2019, (iii) 1,164 shares vest in two equal annual installments on March 2, 2019 and March 2, 2020, (iv) 2,100 shares vest in three equal annual installments on March 8, 2019, March 8, 2020 and March 8, 2021, and (v) 3,424 shares vest in three equal annual installments on March 15, 2019, March 15, 2020, and March 15, 2021, in each case provided that the reporting person remains in continuous service with the issuer as of each vesting date.

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