Alfie Evan Allen (born September 12, 1986) is an English actor, best known for his role as Theon Greyjoy on the HBO fantasy series Game of Thrones (2011–2019), for which he received a nomination for the Primetime Emmy Award for Outstanding Supporting Actor in a Drama Series in 2019. In film, he is best known for his starring roles in John Wick (2014), The Predator (2018), and Jojo Rabbit (2019).

His older sister is singer Lily Allen. Allen's first professional appearance was in a one-off Channel 4 comedy, You Are Here in 1998. The same year, Allen and his sister Lily appeared in the 1998 film, Elizabeth, which was produced by their mother. His early work included small roles in Agent Cody Banks 2: Destination London, Atonement and BBC1's historical hospital drama, Casualty 1907. In 2008, he took over Daniel Radcliffe's role in the stage play, Equus. He has continued to work in films, appearing in Soulboy, The Kid, Freestyle and Powder in 2010. In 2012, he starred in the British thriller, Confine.