The Roman Catholic Diocese of Valleyfield (Latin: Dioecesis Campivallensis) is a Catholic diocese in Quebec and a suffragan of the Archdiocese of Montreal.

[2] The diocese, which is based in the western suburbs of Montreal, features approximately 201,000 baptized Catholics.

Parishioners are served by 48 priests, 17 deacons, 31 religious brothers, and 76 religious sisters.

In 2008, the diocese consolidated its 63 parishes into 24.

This article about a Roman Catholic diocese in Canada is a stub.