O Yeong-su (Korean: 오영수; born O Se-kang, October 19, 1944) is a South Korean actor. He began acting in theatre in 1967, and has, according to himself, appeared in over 200 productions.He later began acting in film and television, often portraying monks due to his experience with Buddhist plays. In 2021, he portrayed Oh Il-nam in the Netflix survival drama Squid Game, which gave rise to his worldwide popularity and won him a Golden Globe Award for Best Supporting Actor in a Series, Miniseries or Television Film, as well as a nomination for the Primetime Emmy Award for Outstanding Supporting Actor in a Drama Series.