The Co-Cathedral of Saint-Antoine-de-Padoue is a co-cathedral in Longueuil, Quebec, Canada, on Montreal's south shore. It is located on the corner of Rue Saint-Charles and Chemin Chambly in the Borough of Le Vieux-Longueuil. It is dedicated to St. Anthony of Padua. The cathedral houses the remains of the Blessed Marie-Rose Durocher, the foundress of the Sisters of the Holy Names of Jesus and Mary.

Longueuil is a city in the province of Quebec, Canada. It is the seat of the Montérégie administrative region and the central city of the urban agglomeration of Longueuil. It sits on the south shore of the Saint Lawrence River directly across from Montreal. The population as of the Canada 2021 Census totalled 254,483, making it Montreal's second largest suburb, the fifth most populous city in Quebec and twentieth largest in Canada.