The unnamed fictional character most frequently referred to as The Man in Black is the main antagonist on the American ABC television series Lost. He appeared primarily as a cloud of black smoke until the final episode of season five where he appeared as a middle-aged man dressed in black. In season six, he primarily appeared in the physical form of John Locke. He exhibited the ability to "scan" the minds and memories of others, allowing him to confront characters such as Mr. Eko and Ben Linus, with "judgement", and to assume the forms and memories of the deceased, starting with the original Man in Black himself, his brother Jacob, or Christian Shephard, Yemi, Alex Rousseau, and Locke. According to Jacob, who explains this to Richard Alpert, it is the incarnation of evil, and its primary goal—to escape from the island—would be the "end of everything good".

Terrance Quinn, known professionally as Terry O'Quinn, is an American actor. He is best known for his Primetime Emmy Award-winning performance of John Locke on the TV series Lost (2004–2010). In film, he is best known for playing the title role in The Stepfather (1987) and Howard Hughes in The Rocketeer (1991), with roles in other films such as Heaven's Gate (1980), Silver Bullet (1985), Young Guns (1988), Blind Fury (1989), Tombstone (1993), and Primal Fear (1996).