The Armed Forces Service Medal is a decoration of the United States military which was created by order of President William J. Clinton in January 1996. The medal is a theater service award which is presented to those service members who engage in "significant activity" for which no other campaign or service medal is authorized.

The term "significant activity" is determined by theater commanders and is normally deemed to be participation in a U.S. military operation considered to hold a high degree of scope, impact, and international significance that the operation warrants the presentation of a permanent service medal. Actions to be considered include peacekeeping operations, prolonged humanitarian actions, or military operations in support (or as a member of) NATO or United Nations forces.

The Armed Forces Service Medal was originally intended to be a replacement for the Armed Forces Expeditionary Medal, however the two decorations are considered separate awards with different award criteria. The primary difference between the two is that the Armed Forces Service Medal is awarded for actions "through which no foreign armed opposition or imminent threat of hostile action was encountered". This definition separates the two medals in that the Armed Forces Expeditionary Medal is normally awarded for combat operations and other combat support missions.

The individual criteria for the Armed Forces Service Medal specify that a service member must perform at least thirty consecutive days in a geographical theater region to qualify for the decoration. Aircrew members may earn the award if a total of thirty mission days was performed flying into and out of the given area.

A service member may not earn both the Armed Forces Expeditionary Medal and Armed Forces Service Medal for the same action nor may a service member earn the Armed Forces Service Medal for humanitarian actions if the action in question qualified for the Humanitarian Service Medal. Additional awards of the Armed Forces Service Medal are denoted by service stars.

See also: Awards and decorations of the United States military