Located at the south-eastern tip of India, the Gulf of Mannar Marine Biosphere Reserve is the first Marine Biosphere Reserve in South and South-East Asia. The Gulf is where the southward extension of the Bay of Bengal meets the Indian Ocean, and is one of the most biologically diverse regions in India. The Site supports 117 species of coral, over 450 of fish including four seahorses, 160 birds, 641 species of crustacean including 38 crabs and two lobsters, four sea turtles, and 11 mangroves. Globally threatened species include the dugong (Dugong dugon), whale shark (Rhincodon typus), green sea turtle (Chelonia mydas), hawksbill turtle (Eretmochelys imbricata) and Indo-Pacific humpback dolphin (Sousa chinensis). The local communities are mainly Marakeyars, with fishing their main livelihood. Although classified as a Marine National Park and recognized as a World Heritage Site, habitat destruction, over-harvesting of marine resources and localized land-based sources of marine pollution have been identified as threats to the ecological integrity of the Site.

Gulf of Mannar Biosphere Reserve (GoMBR), extends between Toothukudi & Ramanathapuram districts; joint declaration of Government of India & Government of Tamil Nadu.