Cornelius O'Brien (4 May 1843 – 9 March 1906) was a Canadian Roman Catholic priest, archbishop, and author of 39 books.

Born in New Glasgow, Prince Edward Island, the son of Terence O'Brien and Catherine O'Driscoll, O'Brien graduated from Urban College and in 1871 was ordained a priest.

He established a Catholic high school (1888) and Holy Heart Seminary (1896), both in Halifax and helped to found the French-language Collège Sainte Anne (1890) in Pointe-de-l'Église, Nova Scotia.

Sir John Thompson, a former Premier of Nova Scotia and the first Catholic Prime Minister of Canada.

This article about a Roman Catholic archbishop from Canada is a stub.