Brendan Gleeson (born 29 March 1955) is an Irish actor. He has received various accolades, including a Primetime Emmy Award, two British Independent Film Awards and three IFTA Awards, along with nominations for an Academy Award, three BAFTA Awards and five Golden Globe Awards. In 2020, he was listed at number 18 on The Irish Times list of Ireland's greatest film actors. He is the father of actors Domhnall Gleeson and Brian Gleeson.

He is known for his supporting roles in films such as Braveheart (1995), Michael Collins (1996), 28 Days Later (2002), Gangs of New York (2002), Cold Mountain (2003), Troy (2004), the Harry Potter film series (2005–2010), Suffragette (2015), Paddington 2 (2017), The Ballad of Buster Scruggs (2018), and The Tragedy of Macbeth (2021). He is also known for his leading roles in films such as The General (1998), In Bruges (2008), The Guard (2011), Calvary (2014), Frankie (2019), and The Banshees of Inisherin (2022) for which he received a nomination for the Academy Award for Best Supporting Actor.

He won a Primetime Emmy Award in 2009 for his portrayal of Winston Churchill in the television film Into the Storm. He also received a Golden Globe Award nomination for his performance as Donald Trump in the Showtime series The Comey Rule (2020). From 2017 to 2019 he starred in the crime series Mr. Mercedes.