Laguna San Ignacio, a UNESCO World Heritage Site, is the most pristine gray whale birthing lagoon on the planet. The 1.5 million acre Laguna San Ignacio Wetland Complex is located on the Pacific Coast of Baja California Sur, Mexico in the municipality of Mulege. The wetland complex extends along 248 miles of coastline, including the lagoon and the Pacific coast of the Baja California Peninsula. It is located within the Vizcaíno Biosphere Reserve and is 600 miles south of the United States–Mexico border.

The Laguna San Ignacio Wetland Complex (LSIWC) includes the lagoon, intertidal mudflats, salt flats, and sandy beaches, halophilic vegetated coastal plains intersected by densely vegetated arroyos all of which rank among the most productive on earth. The LSIWC extends over six ejidos and an area of federal lands. Three mountain ranges surround the lagoon, the Sierra de Santa Clara, the Sierra de San Francisco, and the Sierra de Guadalupe.

The organic productivity (i.e., the amount of life and life-giving nutrients) of the lagoon complex is extraordinarily high. It supports an amazing variety of plants and animals including gray whales, green sea turtles and migratory birds. The lagoon complex also provides critical habitat for rare species such as the endangered Peninsular pronghorn, peregrine falcons, golden and bald eagles, and osprey.

Gray whales migrate from the high Arctic waters of the Bearing and Chukchi Seas to the warm coastal lagoons of Baja California. The protection of the LSWIC is not only crucial for the survival of these cetaceans, but it is also important for the whale watching industry at the lagoon and all over the Baja California Peninsula and the U.S. Pacific Coast.

The LSIWC provides critically important habitat for migratory and waterfowls such as
black brant (Branta bernicla) and godwits (Limosa spp). Ninety-eight species of terrestrial birds and 123 species of waterfowls have been reported on site.

Laguna San Ignacio is divided into northern and southern sections and has three entrances to the Pacific Ocean. The lagoon is relatively shallow (19.7-39.4 ft.) with maximum channel depths of 52.5 feet. Wetlands and mangroves extend along 198 miles of the 247 miles of LSIWC coastline. The mangrove is a salt-tolerant tree that grows in intertidal areas of tropical and subtropical oceans. Mangrove marshes are important bird habitat, breeding and feeding areas, as well as nurseries for many species of ocean fish. The LSIWC include white mangrove (Languncularia racemosa) and red mangrove (Rizophora mangle) species.