Lachlin McCallum (March 15, 1823-January 13, 1903) was a Canadian politician.

McCallum, born in Isle of Tiree, Argyleshire , Scotland, was a contractor and shipowner before entering politics as a Liberal-Conservative. He represented the riding of Monck in the Canadian House of Commons 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.

Due to the closeness of the result, McCallum was unseated on May 12, 1875. In the subsequent byelection, McCallum again defeated Edgar, this time by a mere 4 votes.

McCallum remained in the House until 1887, when he was appointed to the Senate. He died in office in 1903.