(born 12 September 1943) is a Sri Lankan Canadian novelist and poet, perhaps best known for his Booker Prize winning novel adapted into an Academy-Award-winning film, The English Patient.

After relocating to Canada in 1962, Ondaatje became a Canadian citizen. Ondaatje studied for a time at Bishop's University, but moved to Toronto and received his BA from the University of Toronto and his MA from Queen's University in Kingston, Ontario and began teaching at the University of Western Ontario in London, Ontario. In 1970 he settled in Toronto. From 1971 to 1988 he taught English Literature at York University and Glendon College in Toronto.

His style of fiction, introduced in Coming Through Slaughter (1976) and mastered in The English Patient (1992), is non-linear. He creates a narrative by exploring many interconnected snapshots in great detail. Although he is best known as a novelist, Ondaatje's work also encompasses memoir, poetry, and film. His memoir of his Sri Lankan childhood is called Running in the Family (1982). He has published thirteen books of poetry, and won the Governor General's Award for two of them: The Collected Works of Billy the Kid (1970) and There's a Trick With a Knife I'm Learning to Do: Poems 1973-1978 (1979).

The Collected Works of Billy the Kid and Coming Through Slaughter have been adapted for the stage and produced in numerous theatrical productions across North America. Ondaatje's three films include a documentary on fellow poet bp nichol, Sons of Captain Poetry, and The Clinton Special: A Film About The Farm Show, which chronicles a collaborative theatre experience led in 1971 by Paul Thompson of Theatre Passe Muraille. In 2002 he published a non-fiction book, The Conversations: Walter Murch and the Art of Editing Film, which won special recognition at the 2003 American Cinema Editors Awards, as well as a Kraszna-Krausz Book Award for best book of the year on the moving image.

Ondaatje has, since the 1960s, also been involved with Toronto's influential Coach House Books, supporting the independent small press by working as a poetry editor. He is also known for four other works of fiction: