Ownership Submission
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 *
  MAVERICK CAPITAL LTD
2. Date of Event Requiring Statement (Month/Day/Year)
01/18/2008
3. Issuer Name and Ticker or Trading Symbol
Under Armour, Inc. [UA]
(Last)
(First)
(Middle)
300 CRESCENT COURT, 18TH FLOOR, 
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

DALLAS, TX 72501
6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ 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 3,535,520
I
by Portfolio Funds

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
Equity Swap   (2)(3) 01/25/2008 Common Stock 324,770 $ 45.2664 I by Maverick Fund USA, Ltd. (1)
Equity Swap   (4)(5) 03/25/2008 Common Stock 916,240 $ 45.2664 I by Maverick Fund II, Ltd. (1)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
MAVERICK CAPITAL LTD
300 CRESCENT COURT, 18TH FLOOR
DALLAS, TX 72501
    X    
AINSLIE LEE S III
767 FIFTH AVENUE
11TH FLOOR
NEW YORK, NY 10153
    X    
MAVERICK CAPITAL MANAGEMENT LLC
300 CRESENT COURT
18TH FLOOR
DALLAS, TX 72501
    X    

Signatures

/s/ John T. McCafferty, Attorney-in-Fact 01/23/2008
**Signature of Reporting Person Date

/s/ John T. McCafferty, Attorney-in-Fact 01/23/2008
**Signature of Reporting Person Date

/s/ John T. McCafferty, Attorney-in-Fact 01/23/2008
**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) Maverick Capital, Ltd. ("Maverick Capital") is a registered investment adviser under the Investment Advisers Act of 1940, as amended and acts as the investment manager for each of the portfolio funds that directly hold the reported securities. Maverick Capital Management, LLC ("Maverick") is the general partner of Maverick Capital. Lee S. Ainslie III is the manager of Maverick who is granted sole investment decision pursuant to Maverick's limited liability company regulations. Each reporting owner disclaims beneficial ownership of the reported securities except to the extent of its pecuniary interest therein.
(2) On December 19, 2007, Maverick Fund USA, Ltd. ("Maverick USA"), a fund managed by Maverick Capital, entered into an equity swap agreement with an unaffiliated third party with respect to certain public company securities including 324,770 shares of the issuer's common stock at $45.2664 per share (the "Initial Price"). The swap agreement which does not entitle Maverick USA to receive any shares of common stock, matures and will be settled in cash on March 25, 2008. Maverick USA, however, may in its sole discretion elect to settle the swap agreement earlier.
(3) Upon settlement of the swap agreement, either Maverick USA or the counterparty will be obligated to make a payment for each share subject to the swap agreement as follows: (i) if the closing price of the common stock on the settlement date (the "Settlement Price") is greater than the Initial Price, the counterparty will pay to Maverick USA an amount equal to the difference between the Settlement Price and the Initial Price reduced by any accrued interest and (ii) if the Settlement Price is less than the Initial Price, Maverick USA will pay to the counterparty the difference between the Initial Price and the Settlement Price plus any accrued interest. Further, upon settlement of the swap agreement, the counterparty will pay to Maverick USA the equivalent of any dividends paid to the beneficial owners of common stock. Upon settlement, Maverick USA will pay a Libor-based amount calculated on the notional value of the shares underlying the swap agreement on the date it was entered into.
(4) On December 19, 2007, Maverick Fund II, Ltd. ("Maverick II"), a fund managed by Maverick Capital, entered into an equity swap agreement with an unaffiliated third party with respect to certain public company securities including 916,240 shares of the issuer's common stock at $45.2664 per share (the "Initial Price"). The swap agreement, which does not entitle Maverick II to receive any shares of common stock, matures and will be settled in cash on March 25, 2008. Maverick II, however, may in its sole discretion elect to settle the swap agreement earlier.
(5) Upon settlement of the swap agreement, either Maverick II or the counterparty will be obligated to make a payment for each share subject to the swap agreement as follows: (i) if the closing price of the common stock on the settlement date (the "Settlement Price") is greater than the Initial Price, the counterparty will pay to Maverick II an amount equal to the difference between the Settlement Price and the Initial Price reduced by any accrued interest and (ii) if the Settlement Price is less than the Initial Price, Maverick II will pay to the counterparty the difference between the Initial Price and the Settlement Price plus any accrued interest. Further, upon settlement of the swap agreement, the counterparty will pay to Maverick II the equivalent of any dividends paid to the beneficial owners of common stock. Upon settlement, Maverick II will pay a Libor-based amount calculated on the notional value of the shares underlying the swap agreement on the date it was entered into.

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