Jack Gleeson (born 20 May 1992) is an Irish actor who is best known for his critically acclaimed performance as Joffrey Baratheon on the HBO television series Game of Thrones (2011–2014). Following this role, Gleeson semi-retired from acting and has since taken part in independent theatre and the 2020 BBC miniseries Out of Her Mind.

Gleeson was born in Cork, Ireland, and raised in Ranelagh, Dublin, where he attended Gonzaga College. He has two older sisters, Rachel and Emma, who are also involved in Irish theatre.[1] He attended drama classes with them when he was young, and also performed in youth theatre.

Gleeson attended Trinity College Dublin between 2010 and 2015.[2] He studied philosophy and theology and was elected a scholar at the university in 2012.[3][4][5] At Trinity, Gleeson was a member of DU Players, where he met his future co-founders of Collapsing Horse Theatre Company.