Armand Douglas Hammer (born August 28, 1986) is an American actor. The son of businessman Michael Armand Hammer and the great-grandson of oil tycoon Armand Hammer, he began his acting career with guest appearances in several television series. Hammer's first leading role was as Billy Graham in the 2008 film Billy: The Early Years, and he gained wider recognition for his portrayal of the twins Cameron and Tyler Winklevoss in David Fincher's biographical drama film The Social Network (2010), for which he won the Toronto Film Critics Association Award for Best Supporting Actor.
Hammer went on to portray Clyde Tolson in the biopic J. Edgar (2011), play the title character in the western The Lone Ranger (2013), and star as Illya Kuryakin in the action film The Man from U.N.C.L.E. (2015). In 2017, he starred in Luca Guadagnino's romantic drama Call Me by Your Name, for which he received a nomination for the Golden Globe for Best Supporting Actor and a nomination for the Independent Spirit Award for Best Supporting Male. The following year, he portrayed Martin D. Ginsburg in the biopic On the Basis of Sex (2018). On Broadway theatre, he starred in a production of Straight White Men in 2018.