Kieran O'Brien

In 2013, O'Brien toured the UK in a stage production of Simon Beaufoy's 1997 comedy-drama film The Full Monty, in which he plays the "absurdly over-endowed" guy.

In 2004, O'Brien appeared in the controversial film 9 Songs. According to The Guardian, 9 Songs was the most sexually explicit mainstream film to date, largely because it includes several scenes of real sexual acts between the two lead actors. His role is highly unusual in that he had unsimulated and very graphic sex with his co-star Margo Stilley, including genital fondling, female masturbation with and without a vibrator, penetrative vaginal sex, cunnilingus, footjob and fellatio. During a scene in which Stilley stimulates his penis with her hand after performing fellatio on him, he became the only mainstream British actor who has been shown ejaculating in a mainstream UK-produced feature.

In 1999, O'Brien appeared in his first feature film, Virtual Sexuality. In 2001 he played the role of Private Allen Vest in HBO's acclaimed series Band of Brothers where he played a prominent part in the episode 'The Last Patrol'. He also appeared in the 2002 film 24 Hour Party People. In 2003 he appeared in the Cooper Temple Clause music video "Promises, Promises" and can be seen saying he got 'laid' in the Millennium Dome in the making of the video.

O'Brien was in a relationship with Brookside actress Nicola Stephenson for eight years until 1999.

In 1993, he played the role of Joe Egerton and then Craig Lee in Coronation Street and then the role of Lee Jones in Children's Ward. In 1993 he also became a regular in the detective series Cracker, as the titular character's son.