The Bay of Bengal, the largest bay in the world, forms the northeastern part of the Indian Ocean. Roughly triangular in shape, it is bordered mostly by India and Sri Lanka to the west, Bangladesh to the north, and Burma (Myanmar) and the Andaman and Nicobar Islands to the east.

The Bay of Bengal occupies an area of 2,172,000 km². A number of large rivers – the Padma (a distributary of the Ganges), Meghna (a distributary of the Brahmaputra), Jamuna (a branch of the Brahmaputra), Ayeyarwady, Godavari, Mahanadi, Krishna and Kaveri – flow into the Bay of Bengal. Among the important ports are Cuddalore, Ennore, Chennai, Karaikal, Pondicherry, Tuticorin, Kakinada, Machilipatnam, Vishakhapatnam, Gangavaram, Krishnapatnam, Paradip, Kolkata, Mongla, Chittagong and Yangon.

The International Hydrographic Organization defines the limits of the Bay of Bengal as follows:

On the East. A line running from Cape Negrais (16°03'N) in Burma through the larger islands of the Andaman group, in such a way that all the narrow waters between the islands lie to the Eastward of the line and are excluded from the Bay of Bengal, as far as a point in Little Andaman Island in latitude 10°48'N, longitude 92°24'E and thence along the Southwest limit of the Burma Sea [A line running from Oedjong Raja (5°32′N 95°12′E / 5.533°N 95.2°E / 5.533; 95.2) in Sumatra to Poeloe Bras (Breuëh) and on through the Western Islands of the Nicobar Group to Sandy Point in Little Andaman Island, in such a way that all the narrow waters appertain to the Burma Sea].