John William Mackail OM (26 August 1859 – 13 December 1945) was a Scottish academic of Oxford University and reformer of the British education system. He is most often remembered as a scholar of Virgil or as the official biographer of the socialist artist William Morris, of whom he was a friend. Mackail was Oxford Professor of Poetry from 1906 to 1911, and President of the British Academy from 1932 to 1936.