Sebastian Stan (born August 13, 1982) is a Romanian and American actor and producer. He gained recognition for his role as Bucky Barnes / Winter Soldier in the Marvel Cinematic Universe media franchise, beginning with the film Captain America: The First Avenger (2011), and serving as a lead actor in the Disney+ miniseries The Falcon and the Winter Soldier (2021) and the film Thunderbolts* (2025).

On television, Stan played Carter Baizen in Gossip Girl (2007–2010) and the Mad Hatter in Once Upon a Time (2012), and starred in the miniseries Political Animals (2012). In 2022, he received critical acclaim for his portrayal of Tommy Lee in the Hulu miniseries Pam & Tommy, earning nominations for a Primetime Emmy Award and a Golden Globe Award. On Broadway, Stan has appeared in the Eric Bogosian play Talk Radio (2007) and starred in the William Inge play Picnic (2013).