St. Mary's College is a former high school and junior seminary that was operated by the Congregation of the Most Holy Redeemer, a missionary order of the Catholic Church more commonly known as "Redemptorists."
The school was located on a campus on the north bank of the St. Lawrence River in Maitland, Ontario, several kilometres east of Brockville.
The school functioned as a preparatory college for students initially drawn from Montreal, Prescott and Kirkwood, Missouri under its first Rector, The Reverend Charles Kelz.
[1] For the next 50 years, aside from the juvenate closing temporarily from 1941-1944 because of World War II, St. Mary's College educated nearly 550 boys, constituting nearly every English-speaking Redemptorist in Canada as part of the initial stage in the formation process of training for the priesthood.
One of the primary reasons for declining enrollment at St. Mary's was a 1960 decision by the Ecclesiastical Province of Edmonton to establish a junior seminary, Holy Redeemer College, for training western candidates.