The Korean Service Medal is a decoration of the United States military and was created in November 1950 by order of President Harry Truman. The Korean Service Medal is the primary United States decoration for participation in the Korean War and is awarded to any U.S. service member, who performed duty in the Republic of Korea, between June 27, 1950 and June 27, 1954.

The United States Department of Defense declared thirteen official campaigns of the Korean War, all of which are annotated by service stars on the Korean Service Medal. Some campaigns apply to all branches of the U.S. military, while others are branch specific. Service stars are authorized to the Korean Service Medal for participation in the following campaigns.

• North Korean Aggression (Navy): June 27 to November 2, 1950
• United Nations Defensive (Army, USAF): June 27 to September 15, 1950
• United Nations Offensive (Army, USAF): September 16 to November 2, 1950
• Chinese Communist Forces Intervention (Army, USAF): November 3, 1950 to January 24, 1951
• Communist China Aggression (Navy): November 3, 1950 to January 24, 1951
• Inchon Landing (Navy): September 13 to 17, 1950
• First United Nations Counteroffensive (Army, Navy, USAF): January 25 to April 21, 1951
• Chinese Communist Forces Spring Offensive (Army, Navy, USAF): April 22 to July 8, 1951
• United Nations Summer-Fall Offensive (Army, Navy, USAF): July 9 to November 27, 1951
• Second Korean Winter (Army, Navy, USAF): November 28, 1951 to April 30, 1952
• Korean Defense Summer-Fall, 1952 (Army, Navy, USAF): May 1 to November 30, 1952
• Third Korean Winter (Army, Navy, USAF): December 1, 1951 to April 30, 1953
• Korea, Summer 1953 (Army, Navy, USAF): May 1, 1953 to July 27, 1953

For those service members who participated in the amphibious landing at Inchon, as well as airborne attacks on Sukch'on-Such'on and Musan, an arrowhead device is authorized in addition to campaign service stars.

Although the Korean War ended in 1953, the Korean Service Medal was issued until June of 1954 due to the tense nature of the occupation and garrison duty immediately after the Korean War as well as the high possibility of a renewed attack by North Korea. After 1954, the Korean Service Medal was no longer issued although the Armed Forces Expeditionary Medal was authorized for Korean service in the 1960s. As of 2004, a new medal known as the Korea Defense Service Medal was authorized for all post-Korean War service in the Republic of Korea.

A similar decoration to the Korean Service Medal, known as the Korean War Service Medal, is a foreign medal of South Korea and is awarded to any United States service member who received the Korean Service Medal. The Republic of Korea Presidential Unit Citation is also retroactively authorized to any United States Army veteran who served during the Korean War.