Thomas Bain (December 14 1834 - January 18 1915) was a Canadian parliamentarian.

Bain was born in Scotland and immigrated to Canada with his family when he was three years old where they settled on a bush farm in Wentworth County near Hamilton, Ontario. He was elected to the County Council in the 1860s and became Warden. He was first elected to the Canadian House of Commons in the 1872 Canadian election as a Liberal and was re-elected on six subsequent occasions serving as an MP for 28 years before retiring in 1900. In the House he usually spoke on agricultural issues and became Chairman of the Committee on Agriculture and Colonization in 1896.

When the Speaker of the Canadian House of Commons, James David Edgar, died unexepectedly in July 1899, Wilfrid Laurier asked Bain to become the new Speaker for the remainder of Egar's term.

Bain served as Speaker until the House was dissolved for the 1900 Canadian election in which he did not run.

After retiring from politics, Bain became President of the Landed Banking and Loan Company and the Malcolm and Souter Furniture Company. He died in Dundas, Ontario at age 81.