Secret Reunion (Korean: 의형제; Hanja: 義兄弟; RR: Uihyeongje; lit. "Sworn Brothers" or "Blood Brothers") is a 2010 South Korean action film directed by Jang Hoon, and one of the highest grossing Korean films of 2010. The story follows Song Kang-ho as Agent Lee Han-gyoo of the National Intelligence Service (NIS) who is forced out of his job after failing to stop the assassination of a North Korean dissident. The sleeper cell responsible includes relative newcomer Ji-won played by Gang Dong-won, who gets marked as a traitor when the mission goes south. Six years later, both men are working different jobs when they bump into each other and quickly form a bond.

This is the second film by director Jang Hoon, who completed Rough Cut two years prior.