Joseph Matthew Alwyn (born 21 February 1991) is an English actor. He made his feature film debut as the titular character in Ang Lee's 2016 war drama, Billy Lynn's Long Halftime Walk, and has since played supporting roles in films such as The Favourite (2018), Boy Erased (2018), Mary Queen of Scots (2018), and Harriet (2019). His accolades include a Trophée Chopard, a Critics' Choice Movie Award, a Satellite Award, and a Grammy Award.

Born in Tunbridge Wells, Kent, England, and raised in North London, Alwyn developed an interest in acting during his teenage years and joined the National Youth Theatre in 2009. He acted in two student productions at Edinburgh Festival Fringe, and graduated with a BA degree in English literature and drama from the University of Bristol (2012). He received another BA in acting from the Royal Central School of Speech and Drama (2015). He won the Trophée Chopard at the 2018 Cannes Film Festival, following his appearance in various critically acclaimed films.

Alwyn has also worked with American singer-songwriter Taylor Swift on ten of her songs; he co-wrote tracks such as "Exile", "Betty", "Champagne Problems" and "Coney Island" from Swift's 2020 albums, Folklore and Evermore. "Exile" charted inside the top 10 in eight countries. For his contributions to Folklore, Alwyn won the Album of the Year at the 63rd Annual Grammy Awards. In 2022, he appeared in a lead role of Hulu series Conversations with Friends, starred in the romantic thriller film Stars at Noon, which won the Grand Prix at the 2022 Cannes Film Festival, and featured on the Time 100 Next list.