Bucky Barnes (Marvel Cinematic Universe)

James Buchanan "Bucky" Barnes is a fictional character portrayed by Sebastian Stan in the Marvel Cinematic Universe (MCU) media franchise—based on the Marvel Comics character of the same name. Barnes is childhood best friends with Steve Rogers and serves alongside him in the Howling Commandos during World War II. Barnes is seemingly killed in action, but is actually captured by elements of Hydra within the Soviet Union. He is brainwashed and transformed into a super soldier with a metal arm known as the Winter Soldier. In their quest for world domination, Hydra uses a programmed Barnes as an assassin throughout the 20th century.

Barnes comes into conflict with Rogers and his allies during the Hydra uprising, eventually gaining some control over himself. However, Helmut Zemo later takes control of Barnes to destroy the Avengers. This conflict, along with internal strife over the Sokovia Accords, causes the Avengers to split up and Rogers is forced to hide Barnes in Wakanda, where Shuri eventually cures him of his programming and is given a new code name, White Wolf.

Barnes aids the Avengers in the conflict against Thanos, falling victim to the Blip. After he is restored to life, he joins the final and victorious battle against a variant of Thanos. After Rogers' retirement, Barnes is pardoned by the U.S. government and strives to make amends for his murderous past. He joins Sam Wilson in defeating the pro-Blip Flag Smashers and finds peace with Wilson. Later, Barnes is elected to the United States House of Representatives, and joins the New Avengers.

As of 2025, Barnes has appeared in nine MCU films, as well as in a lead role in the miniseries The Falcon and the Winter Soldier (2021). Stan's portrayal of the character has been met with positive reception. He is the only character who appeared in all four Captain America films.

Alternate versions of Barnes from within the MCU Multiverse appear in the animated series What If...? (2021–2024).