Chilka Lake (Chilika Lake) is a brackish water lagoon, spread over the Puri, Khurda and Ganjam districts of Orissa state on the east coast of India, at the mouth of the Daya River, flowing into the Bay of Bengal. It is the largest coastal lagoon in India and the second largest lagoon in the World. It is the largest wintering ground for migratory birds on the Indian sub-continent. The lake is home to a number of threatened species of plants and animals. The lake is an ecosystem with large fishery resources. It sustains more than 150,000 fisher–folk living in 132 villages on the shore and islands.

The lagoon hosts over 160 species of birds in the peak migratory season. Birds from as far as the Caspian Sea, Lake Baikal, Aral Sea and other remote parts of Russia, Kirghiz steppes of Mongolia, Central and southeast Asia, Ladakh and Himalayas come here. These birds travel great distances, but it must be stressed, that the migratory birds probably follow much longer routes than the straight lines, possibly up to 12,000 km, to reach Chilika River.

In 1981, Chilika Lake was designated the first Indian wetland of international importance under the Ramsar Convention. According to a survey, 45 percent of the birds are terrestrial in nature, 32 percent are waterfowl, and 23 percent are waders. The Lagoon is also home to 14 types of raptors.Around 135 rare and endangered Irrawaddy Dolphins have also been reported. Plus, the lagoon supports about 37 species of reptiles and amphibians. The highly productive chilika lagoon eco-system with its rich fishery resources sustains the livelihood for many fisher men who live in and near the Lagoon. The water spread area of the Lagoon ranges between 1165 to 906 km2 during the monsoon and summer respectively. A 32 km long, narrow, outer channel connects the lagoon to the Bay of Bengal, near the village Motto, recently a new mouth was opened by CDA which has brought a new lease of life to the lagoon. Chilika Lake is the largest wintering ground for migratory birds, on the Indian sub-continent. It is one of thehotspots of biodiversity in the country. Some species listed in the IUCN Red List of threatened animals inhabit the lake for at least part of their life cycle.