An Overseas Service Ribbon is a service military award

Awards and decorations of the United States military

Awards and decorations of the United States Military are military decorations which recognize service and personal accomplishments while a member of the United States armed forces...

 of the United States military which recognizes those service members who have performed military tours of duty outside the borders of the United States of America. There are different versions of the Overseas Service Ribbons for the U.S. Army, U.S. Navy, U.S. Air Force, and the U.S. Coast Guard. U.S. Marines receive the Navy version of the Overseas Service Ribbon.
The Army Overseas Service Ribbon was first issued in August 1981.