William Placid Morris OSB (29 September 1794 – 18 February 1872) was a London-born Roman Catholic bishop.
Morris was ordained a priest of the Order of Saint Benedict on 29 June 1817 and was assigned to missionary work in London, first at the chapel of the Portuguese Embassy in Grosvenor Square, and then, after the closure of that chapel in 1829, in Chelsea. In 1831 he received notice of his appointment as bishop charged with the duty of conducting an Apostolic Visitation into the condition of the Catholic Church on the island of Mauritius where the local clergy had been in conflict with Bishop Edward Bede Slater who, since 1818, had been resident bishop there exercising his duties as Vicar Apostolic of Mauritius and as the first Vicar Apostolic of the Cape of Good Hope. To that end, Morris was appointed Titular Bishop of Troas in October 1831, receiving episcopal ordination on 5 February 1832. His principal consecrator was Bishop James Yorke Bramston assisted by Bishop Peter Augustine Baines, O.S.B., and Bishop Robert Gradwell. The investigation, however, was rendered otiose by the impromptu flight of Slater from Port Louis in June 1832 and his death from exposure a few days later. Instead of investigating Slater, Morris was appointed to succeed him.