Saint-Briac-sur-Mer (French pronunciation: [sɛ̃ bʁijak syʁ mɛʁ], literally Saint-Briac on Sea; Breton: Sant-Briag; Gallo: Saent-Beriac), is a commune in the Ille-et-Vilaine Department in Brittany in northwestern France.

Inhabitants of Saint-Briac-sur-Mer are called briacins in French.

St Briac lies on the Gulf Stream which means it enjoys a warm climate, several degrees warmer than the surrounding areas. The village has fine examples of tropical palms and plants, along the streets, making strolls very enjoyable.

Saint Briac has two campsites, seven beaches, four tennis courts, one soccer field, a yacht club, one mini golf, one 18 hole golf course, and more than 5 restaurants.

The name Saint Briac comes from the name of Saint Briag, an Irishman. Briag arrived from Ireland with Saint Tugdual in around 548.

On 4 and 5 September 1758, a British fleet of 113 ships under the command of Admiral Richard Howe, landed east of the Garde Guerin, in Saint Briac. With a force of more than 12,000 men, under the command of General Thomas Bligh, who accompanied the Duke of York, the future king George III, they established camp in neighboring St Lunaire, but not before pillaging and burning down more than half of Saint Briac.

Le Chateau du Nessay (seen below) was built on an emplacement of a castle originating from the 12th century. During the French Revolution, it was used as a prison, to hold political prisoners.

St Briac was called Port Briac during the French Revolution.