Terrance Quinn (born July 15, 1952), known professionally as Terry O'Quinn, is an American actor. He is best known for his Emmy Award-winning performance as John Locke on the TV series Lost (2004–2010). He had roles in films including The Stepfather (1987), The Rocketeer (1991), Heaven's Gate (1980), Silver Bullet (1985), Young Guns (1988), Blind Fury (1989), Tombstone (1993) and Primal Fear (1996).

Other prominent television roles include Peter Watts in Millennium (1996–1999), FBI Asst. Director Kendall in Alias (2002–2004), Commander Joe White in Hawaii Five-0 (2011–2018), and Tom Tavner in Patriot (2015–2018).