Kenneth is the son of William and Frances Branagh. His father was an Ulster carpenter. Educated in Northern Ireland, he joined the Royal Shakespeare Company in 1984 (after other stage and screen work) and was soon taking on leading roles.
Next, he formed his own 'Renaissance Theatre Company', and then directed and starred in a film version of Shakespeare's 'Henry V' (1989), opposite his first wife, actress and screen writer Emma Thompson. The couple met whilst filming the BBC World War Two period drama Fortunes Of War. They went on to appear in numerous other productions together, including 'Much Ado About Nothing',(1993) where he played Benedick to Thompson's Beatrice and 'Dead Again' (1991) where he starred as American sleuth Mike Church and composer Roman Strauss opposite Thompson's amnesiac Grace and pianist Margaret. They also both starred in 'Peter's Friends,' (1992) a film which reunited Thompson with some of her university friends including Hugh Laurie and Stephen Fry. His mother in law, actress Phyllida Law was also in the film. It was during this time that Kenneth gained substantial public and professional recognition for his innovative work, and he was dubbed the 'new Olivier' by the press. However, the press soon developed a love-hate relationship with Branagh when he published his autobiography at the age of thirty. They did not report that it was done to help fund his film and theatre productions and reviews and press coverage of Branagh became negative and overtly hostile. His 1995 film version of 'Frankenstein' was particularly savaged by the critics. In 1995, he and Thompson divorced.
In recent years he has continued to appear in many diverse roles on stage and screen but taken a less prominant role in the press. In 2002, he played the stern Neville in 'Rabbit Proof Fence', an Australian film about Aboriginal rights. The same year also saw the release of the award winning film 'Shackleton,' which tells the tale of the the South Pole explorer.
Ironically, Branagh has fallen back in favour with the press and many of his films that were dismissed when they were first released are considered classics.
Kenneth married film art director Lindsay Brunnock in 2003.