William Grant Glassco, OC (August 30, 1935 – September 13, 2004) was a Canadian theatre director, producer, translator and founder of Toronto's Tarragon Theatre.
From 1959 to 1964, Glassco taught English at the University of Toronto.
He founded the Tarragon Theatre in 1970 with his wife Jane (née Gordon), and stayed there until 1982.
Later, he became the artistic director of the CentreStage Theatre Company which merged, in 1988, with the Toronto Free Theatre to become CanStage.
He is also known for introducing the English-speaking world (along with co-translator John Van Burek) to the plays of Quebec playwright Michel Tremblay, including Les Belles-sœurs and Albertine in Five Times.