Alexander Thom (October 26, 1775 – September 26, 1845) was a military surgeon, judge and political figure in Upper Canada. He was born in Scotland in 1775, the son of a farmer named Alexander Thom, and studied at King's College in Aberdeen. He died at Perth in 1845. His daughter Harriett married Perth lawyer , the son of judge Henry John Boulton. Another daughter Catherine Rosamund married Chief Justice John Godfrey Spragge.