Olivier Elzéar Mathieu (24 December 1853 – 26 October 1929) was a Canadian Roman Catholic priest, academic, and Archbishop of Regina.

Born in Saint-Roch (Quebec City), the son of Joseph Mathieu and Marguerite Latouche, he studied at the Quebec Seminary and received a Doctor of Theology in 1878 from Université Laval. He was ordained a priest by Cardinal Elzéar-Alexandre Taschereau in 1878 and was appointed professor of philosophy at Laval University.

In 1882, he went to study in Borne, Italy and received a Doctor of Philosophy and Doctor of the Academy of Saint Thomas. Returning to Quebec, he received a Master of Arts in 1889. From 1899 to 1908, he was Rector of Université Laval.

Mathieu was appointed a Companion of the Order of St Michael and St George (CMG) during the visit to Canada of TRH the Duke and Duchess of Cornwall and York (later King George V and Queen Mary) in October 1901.^[1] He was later created a Knight of the Légion d'honneur.

In 1911, he was appointed Bishop of Regina and Archbishop of Regina in 1915.

• "A history of Quebec, its resources and people, Volume 2". Internet Archive. 1908.

• Archbishop Olivier Elzéar Mathieu at Catholic-Hierarchy