Peter Mullan (; born 2 November 1959) is a Scottish actor and filmmaker. He is best known for his role in Ken Loach's My Name Is Joe (1998), for which he won Best Actor Award at 1998 Cannes Film Festival and The Claim (2000). He is also winner of the World Dramatic Special Jury Prize for Breakout Performances at 2011 Sundance Film Festival for his work on Paddy Considine's Tyrannosaur (2011). Mullan appeared as supporting or guest actor in numerous cult movies, including Riff-Raff (1991), Braveheart (1995), Trainspotting (1996), Young Adam (2003), Children of Men (2006), War Horse (2011) and the Harry Potter film series (2010–11).

Mullan is an acclaimed art house movie director. He won a Golden Lion at 59th Venice International Film Festival for The Magdalene Sisters, listed by many critics among the best films of 2003 and nominated for BAFTA Award for Best British Film and European Film Award for best film, and a Golden Shell at San Sebastián International Film Festival for Neds. He is the only person to win top prizes both for acting (Cannes best actor award) and for the best film (Golden lion for The Magdalene Sisters) at major European film festivals.

In television, Mullan appeared in Gerard Lee's and Jane Campion's acclaimed miniseries Top of the Lake as one of the main characters, head of the Mitcham family and father of Tui Mitcham, whose disappearance is the main topic of the series. He was nominated for Primetime Emmy Award for his work in the series. He played a lead role in the 2008 ITV series The Fixer. In 2017, he appeared in the Netflix series Ozark opposite Jason Bateman and Laura Linney. Since 2016, Mullan stars in the BBC Two sitcom Mum. In 2018, he stars in the second season of HBO's Westworld.

Mullan is also politically active, supporting left-wing causes and protests.