Joseph William Gilgun (born 9 March 1984) is an English actor known for several roles, including that of Vinnie O'Neill in the Sky One series Brassic, Eli Dingle in the ITV soap opera Emmerdale, Jamie Armstrong in the long-running ITV soap opera Coronation Street, Woody in the film This Is England (2006) and its subsequent spin-off series, and Rudy Wade in E4's Misfits. From 2016 to 2019, he starred in the AMC television adaptation of the Vertigo comic Preacher as the Irish vampire Cassidy.

Gilgun was born in Chorley, Lancashire, to Judith and Andrew Gilgun. He grew up in Rivington, Lancashire, as part of a working-class family with his two younger sisters, Jennie Seddon and Rosie Thomson. Gilgun attended Rivington VA Primary School and Southlands High School. He has dyslexia and ADHD, which he describes as the "biggest pain of [his] life" and in interviews has openly discussed depression and anxiety. He started drama workshops at the age of eight, following advice from an educational psychologist, and was described as having "exceptional talent". He also trained at the Laine Johnson Theatre School and the Oldham Theatre Workshop. When he was 10, he got his first TV acting role in Coronation Street. He stayed with the show until he was thirteen years old.