vast tract of forest and saltwater swamp forming the lower part of the Padma River (Ganges 【Ganga】 River (Ganges River)) delta, extending roughly 160 miles (260 km) along the Bay of Bengal (Bengal, Bay of) from the Hugli River estuary in India to the western segment of the Meghna River estuary in Bangladesh. The tract reaches inland for about 50 miles (80 km) at its broadest point. A network of estuaries, tidal rivers, and creeks intersected by numerous channels, it encloses flat, marshy islands covered with dense forests.

The name Sundarbans is perhaps derived from the term meaning “forest of sundari,” a reference to the large mangrove trees that are most plentiful in the area. The forest passes into a mangrove swamp along the coast, with many wild animals and crocodile-infested estuaries in its southern region. The area has long had the status of a forest reserve; it also is one of the last preserves of the Bengal tiger (Panthera tigris tigris). In 1997 the mangrove forest of the Sundarbans was designated a UNESCO World Heritage site.