Montague Johnstone Muir Mackenzie (1847–1919), painted here by his daughter Susan Annie Eliza Muir Mackenzie 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. The eighth of ten children he was educated at Charterhouse School between 1860 and 1866 before going up to Hertford College, Oxford University. He graduated with a BA degree in 1870 and became a Fellow. On 17 August 1888, he married the Hon. Sarah Napier Bruce (1856–1931). They had one child, Enid, born on 25 June 1889. Muir Mackenzie was enrolled as a pupil barrister at Lincoln's Inn in January 1869 and called to the bar on 27 January 1873. He held the office of "Bencher" of the Middle Temple and was a member of the South-Eastern Circuit. Muir Mackenzie was joint editor of several legal publications and also had a number of other publications, including Notes on the Temple Organ (1911) of which he was joint author with Edmund Macrory.