13F-HR 1 d13fhr.txt FORM 13F UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 13F FORM 13F COVER PAGE Report for the Calendar Year or Quarter Ended: June 30, 2010 Check here if Amendment [_]; Amendment Number: ---------- This Amendment (Check only one): [_] is a restatement [_] adds new holdings entries. Institutional Investment Manager Filing this Report: Name: Liberty Mutual Insurance Company Address: 175 Berkeley Street Boston, Massachusetts 02116 Form 13F File Number: 28-33 The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete, and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form. Person Signing this Report on Behalf of Reporting Manager: Name: Scott D. Fitzhenry Title: Director of Compliance Phone: 617-357-9500 Signature, Place and Date of Signing: /s/ Scott D. Fitzhenry Boston, Massachusetts August 11, 2010 --------------------------- Report Type (Check one.): [x] 13F HOLDINGS REPORT. (check here if all holdings of this reporting manager are reported in this report). [_] 13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).) [_] 13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).) FORM 13F SUMMARY PAGE Report Summary: Number of Other Included Managers: 0 Form 13F Information Table Entry Total: 471 Form 13F Information Table Value Total: $338,930 (in thousands) List of Other Included Managers: Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report. [If there are no entries in this list, state "NONE" and omit the column heading and list entries.] NONE

LIBERTY MUTUAL INSURANCE CO 13F-HR