Ko Chang-seok (born October 13, 1970) is a South Korean actor. Ko began his career on stage, performing in plays and musicals for many years before moving on to bit parts in films. He once earned his living by working on farms and in iron foundries, then acquired fame through his scene-stealing roles in Jang Hoon's films, notably as the movie director in Rough Cut (2008), and the Vietnamese gang boss in Secret Reunion (2010). He has since become one of the busiest supporting actors in Korean cinema.