Bahía de San Quintín, Protected coastal bay in Baja California, Mexico

Bahía de San Quintín is a coastal lagoon in Baja California, 20 km from the town of San Quintín and 200 km from Ensenada. It forms the eastern part of a larger lagoon split in two, the western part being Bahía Falsa, where oyster farms offer boat tours and shoreline restaurants. Its wetlands are largely protected within the San Quintín Nature Reserve, with easy access at Bahía Falsa and La Chorera.

Spanish expeditions knew the bay as Puerto de la Posesión while Baja California was still thought to be an island. Dominican friars founded the Misión de Santo Domingo de la Frontera near the bay in the late 18th century; distance and epidemics forced one relocation before it was abandoned in the mid-19th century. Colonisation came around 1861, when the opening of the port brought numerous German and English settlers to the land around the lagoon and to the town of San Quintín.

The bay's name comes from the Puerto de la Posesión used by early Spanish expeditions. Since 2015 the annual Festival de las Aves promotes bird protection, and boat tours of the oyster farms in Bahía Falsa let visitors see the harvest work up close.

The bay is accessible via Federal Highway 1 with several lodging options available near the coast. Visitors should prepare for changing weather conditions and plan timing based on local seasonal patterns.

The bay was added to the Ramsar list of wetlands in February 2008, and since 2015 a Bird Festival has been held there every year to promote the protection of its birds. Spanish expeditions knew the inlet as Puerto de la Posesión when Baja California was still thought to be an island.