John William Mackenzie (c. 1845 – 14 October 1914) was a missionary from Nova Scotia to the New Hebrides (now known as Vanuatu). Mackenzie was born in Pictou County, Nova Scotia, and studied at Dalhousie College. He served as a missionary in southern Efate from 1872 to 1912. J. P. MacPhie suggested in 1914 that "his tactfulness has meant much to the whole mission and his saintly character has exercised a unique influence upon Europeans as well as natives." According to J. Graham Miller, Mackenzie is "rightly remembered and honoured" as South Efate's "most eminent missionary".