Collégiale Notre-Dame à Cassel, Medieval church in Cassel, France.

Collégiale Notre-Dame à Cassel is a three-aisled hall church in Gothic style, its naves of equal height, built of brick with iron-sandstone and red Roman tiles in the oldest parts. A square tower rises above the choir. The church was rebuilt in 1290 and restored in the 17th century.

The church was founded in the 10th century and experienced multiple periods of destruction and reconstruction throughout its existence. During the French Revolution, it was repurposed as a stable, prison, and hospital before eventually returning to religious use.

The church takes its name from a 16th-century statue of the Virgin venerated in the crypt of the former Saint-Pierre collegiate church, demolished in 1788; the figure is Cassel's patron and protector. A novena to Notre-Dame de la Crypte is held each year from 2 to 10 July. Until the mid-20th century the town also honoured Saint Roch with a December novena, and a boy from rue Moeneclaye was singled out yearly in memory of the plague miracle.

The church stands on the hilltop of Cassel, and the square tower rises above the choir rather than the entrance, so the facade with the round-arched doorway and steps is not the base of the spire. The novena to Notre-Dame de la Crypte runs each year from 2 to 10 July, when the parish prays for the town's protection.

Marshal Foch prayed daily before the statue of Notre-Dame de la Crypte during World War I, linking his military service with personal devotion. This habit of a celebrated military leader left a lasting mark on how locals remember the church's role during wartime.