William Young Sellar (22 February 1825 – 12 October 1890) was a Scottish classical scholar.
Sellar was born at Morvich, Sutherland, the son of Patrick Sellar of Westfield, Morayshire and his wife Ann Craig of Barmakelty, Moray. He was educated at the Edinburgh Academy and afterwards at the University of Glasgow. He entered Balliol College, Oxford, as a scholar. Graduating with a first-class in classics, he was elected fellow of Oriel, and, after holding assistant professorships at Durham, Glasgow and St Andrews, was appointed professor of Greek at St Andrews (1857). In 1863 he was elected professor of humanity in Edinburgh University, and occupied that chair till his death.
Sellar was one of the most brilliant of modern classical scholars, and was remarkably successful in his endeavours to reproduce the spirit rather than the letter of Roman literature.
Sellar is commemorated with his brother Alexander Craig Sellar, MP for Haddington Burghs and Partick, on the south wall of Balliol College Chapel.
A number of articles on Latin literature (including on Catullus, Roman Literature, Lucretius and Petronius) in the Encyclopædia Britannica, 9th edition, 1875-89.