A winner of the BAFTA Rising Star Award, William Jack Poulter made his feature film debut at the age of 13, in the acclaimed comedy movie Son of Rambow (2007). His performance in the film earned the young actor a British Independent Film Awards nomination for Most Promising Newcomer that year. Following appearances in the fantasy adventure The Chronicles of Narnia: The Voyage of the Dawn Treader (2010) and the crime-comedy Wild Bill (2012), Poulter got his big break when he essayed the role of socially awkward teenager Kenny in the comedy We`re the Millers (2013). In the following year, the actor played Gally in the dystopian science fiction action thriller The Maze Runner (2014), a role he has since reprised in Maze Runner: The Death Cure (2018).

Other significant acting credits include the western epic drama The Revenant (2015), the satirical war movie War Machine (2017), the period crime drama Detroit (2017), The Little Stranger (2018) and Black Mirror: Bandersnatch (2018). His 2019 release includes Midsommar (2019), a horror movie directed by Ari Aster.