Oh Dal-su is a South Korean actor.

Oldboy is a 2003 South Korean action-thriller film directed and co-written by Park Chan-wook. A loose adaptation of the Japanese manga of the same name, the film follows the story of Oh Dae-su, who is imprisoned in a cell that resembles a hotel room for 15 years without knowing the identity of his captor or his captor's motives. When he is finally released, Dae-su finds himself still trapped in a web of conspiracy and violence as he seeks revenge against his enigmatic captor. His quest becomes tied in with romance when he falls in love with a young sushi chef, Mi-do.