The youngest of three children, John Hannah was born April 23, 1962 in East Kilbride, Scotland. He attended Claremont High School in East Kilbride and went on to an apprenticeship as an electrician. After completing his apprenticeship he considered a change of career and attended the Royal Scottish Academy of Music and Drama.
After graduation,John had parts in theatre productions, films, and television but things really turned around for him with his appearance as Matthew in Four Weddings and a Funeral (1994). John was able to do more film work, appearing the following year in three films, Madagascar Skin, The Final Cut, and The Innocent Sleep. After work in a few forgettable pictures and the title role on the British TV series McCallum, Hannah got his next significant role in Peter Howitt's 1998 romantic comedy Sliding Doors. He also starred in the axed U.S. series MDs (2002), as well as guest appearances in Alias (2001), Frasier (2002) and Carnivàle (2002). In 2006 he starred in the drama series New Street Law and Cold Blood.
John is also known for using his status as a celebrity to support charitable causes - supporting the Epilepsy Association of Scotland and as a long-time spokesman for Oxfam's Cut Conflict Campaign.
He has been married to actress Joanna Roth since 1996. They live in London's East End.