Lachlin (Lachlan) McCallum (March 15, 1823 – January 13, 1903) was a Canadian politician. McCallum, born in Tiree, Argyllshire, Scotland, was a contractor and shipowner before entering politics as a Liberal-Conservative. He represented the riding of Monck in the House of Commons of Canada from 1867 to 1872, when he was defeated by James David Edgar. However, in 1874, McCallum defeated Edgar by a margin of just 34 votes, and was returned to Parliament. He served as reeve for the United Townships of Sherbrooke and Moulton in Ontario.