Thomas Underwood (May 6, 1863 – May 10, 1948) was a building developer and the 13th mayor of Calgary, Alberta.

Born in Asfordby, Leicestershire, England in 1863, Underwood emigrated to Canada when he was 20.

Two years later, he joined a Canadian Pacific Railway construction gang and was working in Craigellachie, British Columbia at the time of the last spike was driven to complete the transcontinental railroad.

Underwood spent the first two and a half years working for Jarrett-Cushing Lumber Company.

Underwood was involved in the construction of many of the larger buildings in early Calgary.