Saint-Maur-des-Fossés owes its name to Saint-Maur Abbey, founded in 638 by Queen Nanthild, regent for her son Clovis II, at a place called Fossati in Medieval Latin and Les Fossés in modern French, meaning "the moats".

This place, located at the narrow entrance of a loop where the river Marne made its way round a rocky outcrop,[3] was probably named after the moats of an ancient Celtic oppidum and later a Roman castrum; the site was known in medieval documents as Castrum Bagaudarum, at a time when the marauding Bagaudae had developed a legendary reputation as defenders of Christians against Roman persecution.

[5] In 868, King Charles the Bald invited the monks of the Abbey of Saint-Maur de Glanfeuil (in Le Thoureil, Maine-et-Loire, western France), who had fled their abbey due to Viking invasion, to relocate to Saint Pierre des Fossés with their precious relics of Saint Maurus.

[6] The abbey was secularised in 1535, and in 1541, the architect Philibert Delorme designed a château on the site for Cardinal Jean du Bellay, bishop of Paris, on four ranges of building around a square central court.

On September 23, 1568, her teenage son, King Charles IX, issued the Edict of Saint-Maur, which prohibited all religions but Catholicism.

Building projects at the site were only interrupted by Catherine's death (1589); the château was sold to the Condé family and was eventually completed, and furnished with extensive parterres, at the end of the seventeenth century.

The Château de Saint-Maur, still in the possession of the Condé family, was nationalised during the French Revolution, emptied of its contents, and its terrains divided up among real-estate speculators.

[3] The present territory also includes a formerly distinct village, La Varenne-Saint-Hilaire, against the perimeter of the nearby game preserve of Saint-Hilaire, part of the abbey's domaines.

During the French Revolution, Saint-Maur-des-Fossés was temporarily renamed Vivant-sur-Marne (meaning "Alive upon Marne") in a gesture of rejection of religion.