Sebastian Stan (born August 13, 1982) is a Romanian-American actor. He gained recognition for his role as Bucky Barnes / Winter Soldier in the Marvel Cinematic Universe media franchise, beginning with 2011's Captain America: The First Avenger. He later returned in Captain America: The Winter Soldier (2014), and went on to star in Captain America: Civil War (2016), Avengers: Infinity War (2018), Avengers: Endgame (2019) and The Falcon and the Winter Soldier (2021).

On television, he has played Carter Baizen in Gossip Girl, Prince Jack Benjamin in Kings, Jefferson in Once Upon a Time, and T.J. Hammond in Political Animals. The latter earned him a nomination for the Critics' Choice Television Award for Best Supporting Actor in a Movie/Miniseries. In films, he co-starred in Jonathan Demme's comedy-drama Ricki and the Flash and Ridley Scott's science fiction film The Martian. In 2017, he portrayed Jeff Gillooly in the biopic I, Tonya, and in 2022, he stars in the miniseries Pam & Tommy.