A native of Lewes, Sussex, William Nicholson was raised in a Roman Catholic family in Gloucestershire. By the time he reached his tenth birthday he had decided to become a writer. He was educated at Downside School, Somerset, and Christ's College, Cambridge.
At the start of his career Nicholson worked for the BBC as a director of documentary films with numerous works to his credit between the mid-1970s and mid-1980s. He gained renown as a novelist and playwright when the first book of his popular Wind On Fire trilogy won the Blue Peter best book award and the Smarties Gold Award for best children's book. He has written several novels and fantasy books.
He has twice been nominated for Tony Awards for best play, for Shadowlands and The Retreat from Moscow. He also turned Shadowlands, based on the relationship between C. S. Lewis and Joy Gresham, into a BBC-TV play in 1985, and an acclaimed film in 1993. The latter starred Anthony Hopkins and Debra Winger and was directed by Richard Attenborough. His other screenplays include Nell (1994), First Knight (1995) and Grey Owl (1999). He later worked as a writer on the Academy Award winning epic Gladiator (2000), and wrote and directed the 1997 film Firelight.
In 2007 Nicholson co-wrote the film Elizabeth: The Golden Age, from an earlier script by Michael Hirst.
William Nicholson's first nomination came in 1989 when BAFTA TV Awards included the 1987 teleplay Sweet as You Are, which he co-wrote with Ruth Caleb and Angela Pope, on its list of candidates for 'Best Single Drama'. His next nominations were for 1994's Shadowlands when he was a contender for both a BAFTA and an Oscar for 'Best Adapted Screenplay'. 1997 was another successful year, with an 'Outstanding Writing for a Miniseries or a Special' Emmy nomination for the 1996 TV drama Crime of the Century. He was also singled out at the San Sebastian International Film Festival for Firelight, with a nomination for the 'Golden Seashell' Award and a win of the "Special Prize of the Jury."
2000 turned out to be Nicholson's most impressive year to date, with acclaim for the Best Picture Oscar winner Gladiator. He had nominations for the Sierra Award from the Las Vegas Film Critics Society Awards and the Saturn Award from the Academy of Science Fiction, Fantasy & Horror Films, followed by 'Best Screenplay' nominations from both BAFTA and Oscar.