Gareth Thomas was a Welsh actor best known for the part of Roj Blake in Blake's 7

Thomas trained at RADA and was an Associate Member. He was twice nominated for a BAFTA for his performances in Stocker's Copper (BBC Play for Today) (1972) and Morgan's Boy (1984).

Some of his other television appearances included The Avengers, Coronation Street, Z-Cars, Special Branch, Sutherland's Law, Public Eye, Star Maidens, Who Pays the Ferryman?, Bergerac,By the Sword Divided, The Citadel, Knights of God, Boon, London's Burning, Casualty, Taggart, Heartbeat, Sherlock Holmes, How Green Was My Valley, Torchwood and Midsomer Murders.

Thomas also appeared on stage in many productions. Notable appearances include RSC productions of Twelfth Night, Othello and Anna Christie; English Shakespeare Companyproductions of Henry IV, Part 1 and Part 2 and Henry V; and King Lear, Educating Rita, Cat on a Hot Tin Roof, The Crucible, Equus and DVu. In 2010 Thomas gave an acclaimed performance as Ephraim Cabot in Desire Under the Elms at the New Vic Theatre.

In 2001 he appeared in Storm Warning, an audio drama based on Doctor Who by Big Finish Productions. He also played the part of Kalendorf in the Big Finish Productions Dalek Empireseries. In 2006 he appeared as a guest star in the Doctor Who spin-off series Torchwood, in the episode "Ghost Machine". In 2012, Thomas returned to the role of "Roj Blake" in Big Finish Productions' Blake's 7: The Liberator Chronicles, a series of dramatic readings which take place during Series One before the death of Oleg Gan. Thomas stars as "Blake" in Counterfeit by Peter Anghelides and False Positive by Eddie Robson.

He married three times, having two children from his first marriage, Anna and Glyn; his second wife was make-up artist Sheelagh Wells, and was married to his third wife Linda for some 25 years.