Alexander McMartin (1788–July 12, 1853) was a businessman and political figure in Upper Canada.
He was the first person born in Upper Canada to serve in its Legislative Assembly.
He was born in Charlottenburgh Township in 1788, the son of a United Empire Loyalist who settled on the Raisin River.
McMartin served with the Glengarry militia during the War of 1812 and the Lower Canada Rebellion in 1838.
He also served as justice of the peace, postmaster for Martintown and sheriff for the Eastern District.