Joseph Matthew Alwyn (born 21 February 1991) is an English actor. Alwyn made his feature film debut in a leading role in Ang Lee's war drama Billy Lynn's Long Halftime Walk (2016) and has since appeared in films such as The Favourite (2018), Operation Finale (2018), Mary Queen of Scots (2018), Harriet (2019), Catherine Called Birdy (2022) and The Brutalist (2024), as well as the BBC and Hulu drama series Conversations with Friends (2022).

Born in Kent, he grew up in North London. Alwyn became interested in acting as a teenager. He took part in student productions at the Edinburgh Festival Fringe, earned a bachelor's degree in English literature and drama from the University of Bristol (2012) and in acting from the Royal Central School of Speech and Drama (2015).

He is a Grammy Award winner as a songwriter, received the Chopard Trophy at the 2018 Cannes Film Festival and was named to the Time 100 Next 2022 list of rising stars.