William 'Bill' Gaskill (born 24 June 1930, Shipley, West Yorkshire) is a British theatre director.
He worked alongside Laurence Olivier as a founding director of the National Theatre from its time at the Old Vic in 1963. In 1962, he directed Vanessa Redgrave and Eric Porter in Cymbeline for the Royal Shakespeare Company.
He was the artistic director of the Royal Court Theatre between 1965 and 1972, where he directed premieres of plays by writers including David Hare, John Arden, Edward Bond and Arnold Wesker, as well as introducing many of Bertolt Brecht's works to British audiences.
In 1974 he co-founded the Joint Stock Theatre Company with Max Stafford-Clark, David Hare and David Aukin.
William Gaskill is an associate member of the Royal Academy of Dramatic Art.