Pénestin is located inGuérande Peninsula, 29 km (18 mi) southeast ofVannes and 75 km (47 mi) northwest ofNantes. The mouth of the riverVilaine forms a natural bourndary to the north. Historically, Pénestin belongs toLower Brittany. As Penestin lies on the coast, it boasts several beaches, the most popular of which areLa Mine d'Or andLoscolo.