James Maclennan (March 17, 1833 – June 9, 1915) was a Canadian lawyer, politician, and Puisne judge of the Supreme Court of Canada. Born in the township of Lancaster, Upper Canada (now Ontario), the son of Roderick Maclennan and Mary Macpherson, he received a Bachelor of Arts from Queen's University in 1849. He studied to be a lawyer and was called to the bar in 1857. He practised law with Oliver Mowat in Toronto until 1888, when he was appointed to the Ontario Court of Appeal. He was the editor of The Ontario Judicature Act, 1881 (1884)