Montague Johnstone Muir Mackenzie (29 September 1847 – 18 April 1919) was a Scottish barrister and legal writer. He was the son of Sir John William Pitt Muir Mackenzie of Delvine, Second Baronet and the younger brother of Kenneth Muir Mackenzie, 1st Baron Muir Mackenzie. In his youth, he was a keen sportsman and played football for Scotland in the last of the representative matches played in 1872.