Casey Affleck (born Caleb Casey McGuire Affleck-Boldt; August 12, 1975) is an American actor. He receives various accolades, including an Academy Award, a British Academy Film Award, and a Golden Globe Award. The younger brother of actor Ben Affleck, he began his career as a child actor, appearing in the PBS television film Lemon Sky (1988). He later appeared in three Gus Van Sant films: To Die For (1995), Good Will Hunting (1997), Gerry (2002), and in Steven Soderbergh's Ocean's film series (2001–2007). His first role was in Steve Buscemi's independent comedy-drama Lonesome Jim (2006).

Affleck's breakthrough came in 2007 when he was nominated for the Academy Award for Best Supporting Actor for his performance as Robert Ford in the Western drama The Assassination of Jesse James by the Coward Robert Ford and starred in his brother's crime drama Gone Baby Gone. In 2010, he directed the mockumentary I'm Still Here. He went on to appear in Tower Heist (2011), ParaNorman (2012), and Interstellar (2014), and he received praise for his performance as an outlaw in Ain't Them Bodies Saints (2013).