Denis Thomas O'Connor was a Canadian prelate of the Catholic Church. The first member of the Congregation of St. Basil to become a bishop, he served as Bishop of London (1890-1899) and later as the first Canadian-born Archbishop of Toronto (1899-1908).

The Congregation of St. Basil, also called the Basilians, is a Roman Catholic clerical religious congregation of Pontifical Right for men. It is an apostolic community whose members profess simple vows. The Basilians seek the glory of God, especially in the works of education and evangelization. The congregation was founded in 1822 in the aftermath of the French Revolution. In the early 19th century the Basilian Fathers' educational and pastoral work brought them to a variety of locations in Canada and the United States. In the 1960s, the priests began to minister in Mexico, and in Colombia in the 1980s.