Saint-Marcan (French pronunciation: [sɛ̃ maʁkɑ̃]; Gallo: Saent-Marqaen, Breton: Sant-Marc'han) is a commune in the Ille-et-Vilaine department in Brittany in northwestern France.

Inhabitants of Saint-Marcan are called marcanais in French.

In the heart of the Rosclave Channel in west County Mayo in the Republic of Ireland were the visible the remains of St. Marcin's Castle, Church, outdoor altar and a burial ground.

However, it appears little remains of these features other than on historical maps.

This Ille-et-Vilaine geographical article is a stub.