Australian dramatist and screenwriter known for topical satiric comedies that display his flair for naturalism and local vernacular. He explored the psychology of social interaction, focusing on the social and cultural attitudes of the Australian middle class.

Williamson was reared in Bairnsdale, Victoria, and was educated at the University of Melbourne and Monash University (B.E., 1964). He worked as a design engineer and taught mechanical engineering and psychology before becoming a full-time writer. His Three Plays (1974) includes The Coming of Stork, his farcical first play; Jugglers Three, a black comedy about marital tensions; and What If You Died Tomorrow, an autobiographical work about a novelist dealing with success.

Williamson first earned acclaim with The Removalists (1972; filmed 1975), an absurdist (Absurd, Theatre of the) look at authority, violence, and sexuality; and Don's Party (1973; filmed 1976), about a group of frustrated former radicals. He examines the social dynamics of bureaucracies in The Department (1975) and The Club (1978; filmed 1980). The Perfectionist (1983; filmed 1987) and Emerald City (1987; filmed 1991) are both comedies of manners. Two of Williamson's later plays, Dead White Males (1995) and Heretic (1996), contain historical characters; the former play includes William Shakespeare (Shakespeare, William) in a confrontation with modern-day scholars of his work, and Heretic is Williamson's account of the conflict between anthropologists Margaret Mead (Mead, Margaret) and Derek Freeman over the nature of humanity. Some of his other plays include A Handful of Friends (1976), Travelling North (1980), Top Silk (1989), Money & Friends (1992), Brilliant Lies (1993; filmed 1996), Up for Grabs (2001), and Influence (2005). Williamson also wrote several screenplays, including Phar Lap (1982) and, in collaboration with Peter Weir, Gallipoli (1981) and The Year of Living Dangerously (1982).