Our Lady of Assumption Co-Cathedral, Co-cathedral in Gravelbourg, Saskatchewan, Canada

Our Lady of Assumption Co-Cathedral is a steel-frame church with tan brick walls trimmed in Indiana stone, designed by Montreal architect J. E. Fortin in a mix of Romanesque and Italian Renaissance styles. It measures 54.8 metres long and 19.8 metres high, with twin west towers capped by cupolas reaching 53.3 metres. The interior was decorated by Msgr. Charles Maillard between 1921 and 1931.

The parish church, first dedicated to St. Philomena, was consecrated on 5 November 1919 by Archbishop O. E. Mathieu of Regina, after construction began in 1918 to plans by Montreal architect J. E. Fortin. It became a cathedral on 27 July 1930, was renamed for the Assumption in 1965, and became a co-cathedral in 1998 when Pope John Paul II merged the Diocese of Gravelbourg into the Archdiocese of Regina. Msgr. Charles Maillard decorated the interior between 1921 and 1931.

Originally dedicated to St. Philomena, the church became a cathedral in 1930 and was renamed for the Assumption in 1965. Since 1995 it has formed part of the Gravelbourg Religious Establishments National Historic Site together with the Jésus-Marie convent and the bishop's residence.

The church holds up to 1,500 people, so it is rarely crowded; enter from the west end, where the twin towers and their cupolas rise 53.3 metres. The nave is 15.8 metres high and the transept 25.9 metres wide, giving clear sightlines to the stained glass documented by the Institute for Stained Glass in Canada. The building is a municipal heritage property in Gravelbourg's religious-heritage site.

The interior was updated in the 1960s to meet new requirements following the Second Vatican Council, which changed how Catholic worship was conducted. These modifications reveal how the building adapted to serve its community in a changing era.