Domhnall Gleeson (; born 12 May 1983) is an Irish actor, director and screenwriter. He is the son of actor Brendan Gleeson, with whom he has appeared in a number of films and theatre projects. He received a Bachelor of Arts in Media Arts from Dublin Institute of Technology.

During the early stages of his career, Gleeson directed and wrote several short films, garnered a Tony Award nomination in 2006 for his role in the Broadway production The Lieutenant of Inishmore, and had a supporting role in Never Let Me Go. He became known to a wider audience for his portrayal of Bill Weasley in the Harry Potter film series (2001–2011), along with his father Brendan Gleeson, who played Alastor Moody; Konstantin Levin in Anna Karenina (2012); Tim Lake in About Time (2013); and Russell Allen Phillips in the fact-based war drama Unbroken (2014). Gleeson has won three IFTA Awards for his performances in When Harvey Met Bob (2010), Anna Karenina (2012), and Frank (2014).

In 2015, Gleeson received widespread recognition and praise for his performances in several Academy Award-nominated films: Caleb Smith in Ex Machina, Jim Farrell in Brooklyn, and Captain Andrew Henry in The Revenant. In 2017, he appeared in Mother! alongside his brother Brian Gleeson, co-starred in American Made, and portrayed A. A. Milne in Goodbye Christopher Robin. In 2018, he starred in a live-action adaptation of Peter Rabbit. From 2015 to 2019, Gleeson appeared as General Armitage Hux in the Star Wars sequel trilogy. In 2020, he had a main role in the HBO black comedy series Run. The same year, he was listed at number 21 on The Irish Times list of Ireland's greatest film actors.