Schedule 13G
 
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
 
SCHEDULE 13G
 
 
Under the Securities Exchange Act of 1934
(Amendment No. 04)*
 
Under Armour, Inc. 
(Name of Issuer)
 
Class A Common Stock
(Title of Class of Securities)
 
904311107
(CUSIP Number)
 
Calendar Year 2010
(Date of Event Which Requires Filing of this Statement)
 
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
 
     x  Rule 13d-1(b)
 
     o  Rule 13d-1(c)
 
     o  Rule 13d-1(d)
 
* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.
 
The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).
 
 
 
 
 
CUSIP No.  904311107      
 
      
1 NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
 BAMCO INC /NY/
521990078
   
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

 (a)   o
 (b)   x
   
3 SEC USE ONLY
  
  
   
4 CITIZENSHIP OR PLACE OF ORGANIZATION
  
 New York
    
NUMBER OF SHARES BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH: 5 SOLE VOTING POWER
  
 0
   
6 SHARED VOTING POWER
  
 1,643,200
   
7 SOLE DISPOSITIVE POWER
  
 0
   
8 SHARED DISPOSITIVE POWER
  
 1,981,200
   
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
  
 1,981,200
   
10 CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
  
 o
   
11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
  
 5.15%
   
12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
  
 IA ,  CO
 

FOOTNOTES
  
 
 
 
 
 
CUSIP No.  904311107      
 
      
1 NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
 Baron Capital Group, Inc.
521990078
   
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

 (a)   o
 (b)   x
   
3 SEC USE ONLY
  
  
   
4 CITIZENSHIP OR PLACE OF ORGANIZATION
  
 New York
    
NUMBER OF SHARES BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH: 5 SOLE VOTING POWER
  
 0
   
6 SHARED VOTING POWER
  
 1,840,644
   
7 SOLE DISPOSITIVE POWER
  
 0
   
8 SHARED DISPOSITIVE POWER
  
 2,189,655
   
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
  
 2,189,655
   
10 CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
  
 o
   
11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
  
 5.69%
   
12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
  
 HC ,  CO
 

FOOTNOTES
  
 
 
 
 
 
CUSIP No.  904311107      
 
      
1 NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
 Baron Growth Fund
521990078
   
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

 (a)   o
 (b)   x
   
3 SEC USE ONLY
  
  
   
4 CITIZENSHIP OR PLACE OF ORGANIZATION
  
 New York
    
NUMBER OF SHARES BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH: 5 SOLE VOTING POWER
  
 0
   
6 SHARED VOTING POWER
  
 1,500,000
   
7 SOLE DISPOSITIVE POWER
  
 0
   
8 SHARED DISPOSITIVE POWER
  
 1,500,000
   
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
  
 1,500,000
   
10 CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
  
 o
   
11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
  
 3.90%
   
12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
  
 IV
 

FOOTNOTES
  
 
 
 
 
 
CUSIP No.  904311107      
 
      
1 NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
 Baron Capital Management, Inc.
521990078
   
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

 (a)   o
 (b)   x
   
3 SEC USE ONLY
  
  
   
4 CITIZENSHIP OR PLACE OF ORGANIZATION
  
 New York
    
NUMBER OF SHARES BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH: 5 SOLE VOTING POWER
  
 0
   
6 SHARED VOTING POWER
  
 197,444
   
7 SOLE DISPOSITIVE POWER
  
 0
   
8 SHARED DISPOSITIVE POWER
  
 208,455
   
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
  
 208,455
   
10 CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
  
 o
   
11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
  
 0.54%
   
12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
  
 IA ,  CO
 

FOOTNOTES
  
 
 
 
 
 
CUSIP No.  904311107      
 
      
1 NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
 Ronald Baron
521990078
   
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

 (a)   o
 (b)   x
   
3 SEC USE ONLY
  
  
   
4 CITIZENSHIP OR PLACE OF ORGANIZATION
  
 New York
    
NUMBER OF SHARES BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH: 5 SOLE VOTING POWER
  
 0
   
6 SHARED VOTING POWER
  
 1,840,644
   
7 SOLE DISPOSITIVE POWER
  
 0
   
8 SHARED DISPOSITIVE POWER
  
 2,189,655
   
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
  
 2,189,655
   
10 CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
  
 o
   
11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
  
 5.69%
   
12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
  
 HC ,  IN
 

FOOTNOTES
  
 
 
 
 
 
Item 1.

 
(a)
Name of Issuer
 
 
Under Armour, Inc.

 
(b)
Address of Issuer’s Principal Executive Offices
 
 
1020 Hull Street
Baltimore, MD 21230

Item 2.

 
(a)
Name of Person Filing
 
 
Baron Capital Group, Inc. ("BCG")
BAMCO, Inc. ("BAMCO")
Baron Capital Management, Inc. ("BCM")
Baron Growth Fund ("BGF")
Ronald Baron ("RB")

 
(b)
Address of Principal Business Office or, if none, Residence
 
 
767 Fifth Avenue
49th Floor
New York, NY 10153

 
(c)
Citizenship
 
 
BCG, BAMCO, and BCM are New York corporations. BGF is a series of a Massachusetts business trust. Ronald Baron is a citizen of the United States.

 
(d)
Title of Class of Securities
 
 
Class A Common Stock

 
(e)
CUSIP Number
 
 
904311107

 
Item 3.
If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

 
(a)
o
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

 
(b)
o
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

 
(c)
o
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

 
(d)
x
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C 80a-8).

 
(e)
x
An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

 
(f)
o
An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

 
(g)
x
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

 
(h)
o
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

 
(i)
o
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

 
(j)
o
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J).

 
(k)
o
A group, in accordance with § 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:

 
 
 
 
 
Item 4.
Ownership.
 
Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

 
(a)
Amount beneficially owned: 2,189,655

 
(b)
Percent of class: 5.69

 
(c)
Number of shares as to which the person has:

 
(i)
Sole power to vote or to direct the vote: 0

 
(ii)
Shared power to vote or to direct the vote: 1,840,644

 
(iii)
Sole power to dispose or to direct the disposition of: 0

 
(iv)
Shared power to dispose or to direct the disposition of: 2,189,655

Item 5.
Ownership of Five Percent or Less of a Class
 
If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following o .
 
N/A
 
Item 6.
Ownership of More than Five Percent on Behalf of Another Person.
 
The advisory clients of BAMCO and BCM have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Issuer's common stock in their accounts. To the best of the Filing Persons' knowledge, no such person has such interest relating to more than 5% of the outstanding class of securities.
 
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company
 
BAMCO and BCM are subsidiaries of BCG. BGF is an advisory client of BAMCO. Ronald Baron owns a controlling interest in BCG.
 
Item 8.
Identification and Classification of Members of the Group
 
See Item 3.
 
Item 9.
Notice of Dissolution of Group
 
Not applicable.
 
 
 
 
 
 
Item 10.
Certification
  
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.
 
 

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
 
 
 BAMCO, Inc.
 
    
Date: February 14, 2011
By:
/s/  Ronald Baron 
   Name: Ronald Baron 
   Title:  Chairman and CEO 
    
 
 
 
 Baron Capital Group, Inc.
 
    
Date: February 14, 2011
By:
/s/  Ronald Baron 
   Name: Ronald Baron 
   Title:  Chairman and CEO 
    
 
 
 
 Baron Capital Management, Inc.
 
    
Date: February 14, 2011
By:
/s/  Ronald Baron 
   Name: Ronald Baron 
   Title:  Chairman and CEO 
    
 
 
 
 Baron Growth Fund
 
    
Date: February 14, 2011
By:
/s/  Ronald Baron 
   Name: Ronald Baron 
   Title:  CEO 
    
 
 
 
 Ronald Baron
 
    
Date: February 14, 2011
By:
/s/  Ronald Baron 
   Name: Ronald Baron 
   Title:  Individually 
    
 
Footnotes:

Attention:
Intentional misstatements or omissions of fact constitute Federal criminal violations (See 18 U.S.C. 1001)