The Meritorious Service Medal (MSM) is a military award presented to members of the United States Armed Forces who distinguished themselves by outstanding meritorious achievement or service to the United States subsequent to January 16, 1969.

The MSM was previously awarded as a decoration for achievement during peacetime, but effective September 11, 2001 this decoration may also be bestowed in lieu of the Bronze Star Medal for meritorious achievement in a designated combat theater. Normally, the acts or services rendered must be comparable to that required for the Legion of Merit but in a duty of lesser, though considerable, responsibility. Within the U.S. Army, according to AR 600-8-22, Paragraph 3-16, the MSM may not be upgraded to or downgraded from a recommended Bronze Star Medal. In the Army, an MSM recommendation that is downgraded will be approved as an Army Commendation Medal (ARCOM).

A higher award and decoration, the Defense Meritorious Service Medal (DMSM), is intended for similar services performed under joint duty within the United States Department of Defense, to include the Joint Staff, the Unified Combatant Commands, and joint task forces under their cognizance.