Berthier-sur-Mer (French pronunciation: [bɛʁtje syʁ mɛʁ], lit.

It is located on the south shore of the Saint Lawrence River, east of Quebec City on Route 132.

Berthier-sur-Mer was named after Alexandre Berthier, a captain in the Carignan-Salières Regiment, who was given title to this area in 1672, then known as the seigneury of Berthier-en-bas.

During the 19th century, Irish immigrants were quarantined at nearby Grosse Isle, now a National Historic site.

A strip of rather interesting underlying sedimentary bedrock maintains a relatively straight shoreline through which a natural harbour, quite round in shape, has been eroded.