For the American politician, see Tommy Thompson.

Thomas John Thomson (August 5, 1877 - July 8, 1917) was an influential Canadian artist in the early 20th century.

Born near Claremont, Ontario , he grew up in Leith, near Owen Sound. In 1899 he unsuccessfully tried to volunteer to fight in the Boer War, and instead went to a business college in Seattle, Washington. In 1904 he returned to Canada, and in 1907 joined an artistic design firm in Toronto where many of the future members of the Group of Seven (artists) also worked. With his colleagues he often travelled around Canada, especially to the wilderness of northern Ontario, which was a major source of inspiration for Thomson. His first exhibition was in 1913.

Beginning in 1914 he acted as fire fighter and guide in Algonquin Park in northern Ontario. During the next three years he produced many of his most famous works, including The Jack Pine and The West Wind. However, during a canoeing trip in July of 1917, he disappeared, and his body was discovered on July 17. The official cause of death was drowning, but there are still questions about how he actually died. He was buried at Canoe Lake in Algonquin Park, but at the request of his family his body was reinterred in the family plot beside Leith United Church. An historical marker concerning Tom Thomson was moved to the grave yard in the summer of 2004 from its earlier location nearer the centre of Leith. In 1967 the Tom Thomson Memorial Art Gallery opened in Owen Sound. Numerous examples of his work are on display at the McMichael Canadian Art Collection in Kleinburg, Ontario and at the National Gallery in Ottawa, Ontario.

He is often thought of as a member of the Group of Seven, although the Group was not officially founded until after Thomson's death. Nevertheless, his paintings are representative of the Group's style.

In 1970, Judge William Little published a book, The Tom Thomson Mystery.