Gillen is the current host of Other Voices. He has won two Irish Film & Television Awards and has been nominated for a British Academy Television Award, a British Independent Film Award, and a Tony Award.
Gillen was born in Drumcondra, Dublin. He was educated at St. Vincent's C.B.S. in Glasnevin. He began his acting career as a teenager with the Dublin Youth Theatre, playing Nick Bottom in A Midsummer Night's Dream at the Project Arts Centre before moving to London.
Gillen played Stuart Alan Jones in the groundbreaking Channel 4 television series Queer as Folk, and its sequel, for which he received a British Academy Television Awardnomination for Best Actor. He was nominated for a Tony Award for his highly acclaimed Broadway role in Harold Pinter's play The Caretaker, and has also been nominated for an Irish Times Theatre Award for his portrayal of Teach in the Dublin Gate Theatre's 2007 production of David Mamet's American Buffalo.
In 2004, having been spotted by producers in The Caretaker, Gillen portrayed Tommy Carcetti in the acclaimed HBO series The Wire, for which he received an Irish Film & Television Award for Best Actor in a Lead Role in Television. In 2008, he was named an "Irish cult hero" by the Sunday Tribune. He appeared in the 2009 film 12 Rounds, and in July of that year, he appeared in the one-off BBC2 drama Freefall. He co-starred as Phil Hendrick in the British drama Thorne.
In 2011, Gillen began playing Petyr "Littlefinger" Baelish on the award-winning HBO series Game of Thrones, for which he received his second Irish Film & Television Award nomination. To date he has appeared in all four broadcast seasons, and will reprise the role once more in Season 5. He starred with as cop killer Barry Weiss in the British crime-thriller Blitz, and in the British horror film Wake Wood. He played crime boss John Boy in the acclaimed Irish crime-drama Love/Hate, for which he received his third Irish Film & Television Award nomination and second win.
In 2012, Gillen played CIA Agent Bill Wilson in the opening of The Dark Knight Rises and starred in the British spy-drama Shadow Dancer. He was announced as the new host of the music show Other Voices. He is set to star in the comedy-drama Calvary and the BBC five-part thriller Mayday. He shared a Screen Actors Guild Award nomination with the cast of Game of Thrones for Outstanding Performance by an Ensemble in a Drama Series. He also starred in the short film Ekki Múkk, created for the Valtari Mystery Film Experiment by Icelandic band Sigur Rós.
In 2001, Gillen married Olivia O'Flanagan. The couple live in Ireland with their children Berry and Joe. In 2009, when Gillen won an Irish Film and Television Award for his role in The Wire, he dedicated the award to his wife and children, whom Wilson has stated "were a big motivation for him." His sister, Fionnuala Murphy, is an actress, while his brother, John Paul Murphy, is a playwright, and another sister, Patricia Murphy, is a teacher.