Saint-Nazaire (French pronunciation: ​[sɛ̃.na.zɛʁ]; Breton:Sant-Nazer/Señ Neñseir; Gallo: Saint-Nazère/Saint-Nazaer) is a commune in the Loire-Atlantique department in western France, in traditional Brittany.

The town has a major harbour, on the right bank of the Loire River estuary, near the Atlantic Ocean. The town is at the south of the second-largest swamp in France, called "la Brière". Given its location, Saint-Nazaire has a long tradition of fishing and shipbuilding.