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 *
  MARCATO CAPITAL MANAGEMENT LLC
 2. Date of Event Requiring Statement (Month/Day/Year)
02/27/2013		 3. Issuer Name and Ticker or Trading Symbol
CyrusOne Inc. [CONE]
(Last)
(First)
(Middle)
ONE MONTGOMERY STREET, SUITE 3250		 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)

SAN FRANCISCO, CA 94104		 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, $0.01 par value per share 2,335,226
I
See Footnote (1)

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
MARCATO CAPITAL MANAGEMENT LLC
ONE MONTGOMERY STREET
SUITE 3250
SAN FRANCISCO, CA 94104		     X    
McGuire Richard
ONE MONTGOMERY STREET
SUITE 3250
SAN FRANCISCO, CA 94104		     X    
Marcato International Master Fund, Ltd.
C/O OGIER FIDUCIARY SERVICES (CAYMAN)LTD
89 NEXUS WAY, CAMANA BAY
GRAND CAYMAN, E9 KY1-9007		     X    
Marcato, L.P.
ONE MONTGOMERY STREET
SUITE 3250
SAN FRANCISCO, CA 94104		     X    
Marcato II, L.P.
ONE MONTGOMERY STREET
SUITE 3250
SAN FRANCISCO, CA 94104		     X    

Signatures

Marcato Capital Management LLC, By: /s/ Richard McGuire III; Richard McGuire III, Managing Member 03/28/2013
**Signature of Reporting Person Date
/s/ Richard McGuire III 03/28/2013
**Signature of Reporting Person Date
Marcato International Master Fund, Ltd., By: /s/ Richard McGuire III, Director 03/28/2013
**Signature of Reporting Person Date
Marcato, L.P., By: /s/ Richard McGuire III, Director 03/28/2013
**Signature of Reporting Person Date
Marcato II, L.P., By: /s/ Richard McGuire III, Director 03/28/2013
**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) The securities are held in the account of Marcato International Master Fund, Ltd., Marcato, L.P. and Marcato II, L.P. (collectively, the "Funds") and may be deemed to be beneficially owned by (i) Marcato Capital Management LLC, the investment manager or general partner, as applicable, of the Funds, and (ii) Richard McGuire III, the managing member of Marcato Capital Management LLC. Each of Marcato Capital Management LLC and Richard McGuire III disclaims beneficial ownership of these reported securities except to the extent of its pecuniary interest therein, and this report shall not be deemed an admission that any such person is the beneficial owner of these securities for purposes of Section 16 of the U.S. Securities Exchange Act of 1934, as amended, or for any other purpose.

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