UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the
Securities Exchange Act of 1934 (Amendment No. )

☑ Filed by the Registrant ☐ Filed by a Party other than the Registrant      

CHECK THE APPROPRIATE BOX:
☐   Preliminary Proxy Statement
☐ Confidential, For Use of the Commission Only (as permitted by Rule 14a-6(e)(2))
☐ Definitive Proxy Statement
☑   Definitive Additional Materials
☐ Soliciting Material Under Rule 14a-12

Iron Mountain Inc.

(Name of Registrant as Specified In Its Charter)
(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

PAYMENT OF FILING FEE (CHECK THE APPROPRIATE BOX):
☑   No fee required.
☐ Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.
1) Title of each class of securities to which transaction applies:
2) Aggregate number of securities to which transaction applies:
3) Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (set forth the amount on which the filing fee is calculated and state how it was determined):
4) Proposed maximum aggregate value of transaction:
5) Total fee paid:
☐ Fee paid previously with preliminary materials:
☐ Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the form or schedule and the date of its filing.
1) Amount previously paid:
2) Form, Schedule or Registration Statement No.:
3) Filing Party:
4) Date Filed:

*** Exercise Your Right to Vote ***
Important Notice Regarding the Availability of Proxy Materials for the
Stockholder Meeting to Be Held on May 22, 2019.

IRON MOUNTAIN INCORPORATED



IRON MOUNTAIN INCORPORATED
INVESTOR RELATIONS
ONE FEDERAL STREET
BOSTON, MA 02110

Meeting Information
Meeting Type: Annual Meeting
For holders as of: March 25, 2019
Date: May 22, 2019 Time:   9:00 A.M. U.S. Eastern Time
Location:      Sullivan & Worcester LLP
One Post Office Square
21st Floor
Boston, MA 02109

You are receiving this communication because you hold shares in the company named above.

This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side).

We encourage you to access and review all of the important information contained in the proxy materials before voting.

See the reverse side of this notice to obtain proxy materials and voting instructions.























— Before You Vote —
How to Access the Proxy Materials
Proxy Materials Available to VIEW or RECEIVE:
1. Notice and Proxy Statement      2. Annual Report
How to View Online:
Have the information that is printed in the box marked by the arrow ➔XXXX XXXX XXXX XXXX (located on the following page) and visit: www.proxyvote.com.
How to Request and Receive a PAPER or E-MAIL Copy:
If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for r equesting a copy. Please choose one of the following methods to make your request:
1) BY INTERNET: www.proxyvote.com
2) BY TELEPHONE:     1-800-579-1639
3) BY E-MAIL*: sendmaterial@proxyvote.com
* If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow ➔XXXX XXXX XXXX XXXX  (located on the following page) in the subject line.
Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 8, 2019 to facilitate timely delivery.

— How To Vote —
Please Choose One of the Following Voting Methods

Vote In Person: Many stockholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares.

Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow ➔XXXX XXXX XXXX XXXX  (located on the following page) available and follow the instructions.

Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card.





























Voting Items
The Board of Directors recommends you vote FOR the following:
1.        For the election of twelve (12) directors to the Iron Mountain Incorporated Board of Directors for a one-year term or until their successors are elected and qualified.
Nominees:
1a.       Jennifer Allerton
1b. Ted R. Antenucci
1c. Pamela M. Arway
1d. Clarke H. Bailey
1e. Kent P. Dauten
1f. Paul F. Deninger
1g. Monte Ford
1h. Per-Kristian Halvorsen
1i. William L. Meaney
    1j.   Wendy J. Murdock
    1k.   Walter C. Rakowich
    1l.   Alfred J. Verrecchia
The Board of Directors recommends you vote FOR proposals 2 and 3.
2.       The approval of a non-binding, advisory resolution approving the compensation of our named executive officers as described in the Iron Mountain Incorporated Proxy Statement.
3. The ratification of the selection by the Audit Committee of Deloitte & Touche LLP as Iron Mountain Incorporated's independent registered public accounting firm for the year ending December 31, 2019.
NOTE: In their discretion, the proxies are authorized to vote upon such other business as may properly come before the Annual Meeting of Stockholders or any postponement or adjournment thereof.