The Joint Advisory Commission, Korea (JACK; ) was a U.S. covert operations unit that participated in the Korean War.
Operating under the direction of the Central Intelligence Agency, JACK was responsible for inserting and extracting U.S.-trained Korean agents into North Korea, conducting covert maritime raids along the North Korean coast, and providing escape and evasion support for downed Air Force pilots.
Yong-do Group () based in Yeongdo District, Busan was the main guerrilla unit.