Secret (Korean: 시크릿) is a 2009 South Korean crime thriller film directed by Yoon Jae-goo, starring Cha Seung-won, Song Yoon-ah and Ryu Seung-ryong.

A year earlier, he'd had an affair with his colleague's wife and, slightly drunk on his way back from meeting her, had caused his daughter's death in a car accident.

Wracked with guilt but unable to explain what had happened on that day, he is no longer on speaking terms with his wife, Ji-yeon, who obviously blames him for their only child's death.

One day, Ji-yeon goes out all dressed up but comes home unexpectedly disheveled and with blood spatters on her blouse but refusing to explain herself.

Seong-yeol is called out to investigate the murder of a man with gang connections and is horrified to find trace evidence that hints at his wife's presence at the scene.