The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman and Nicobar Islands of India. Its southern limit is a line between Sangaman Kanda, Sri Lanka, and the north westernmost point of Sumatra, Indonesia. It is the largest water region called a bay in the world. There are countries dependent on the Bay of Bengal in South Asia and Southeast Asia. During the existence of British India, it was named the Bay of Bengal after the historic Bengal region. At the time, the Port of Kolkata served as the gateway to the Crown rule in India. Cox's Bazar, the longest sea beach in the world and Sundarbans, the largest mangrove forest and the natural habitat of the Bengal tiger, are located along the bay.

The Bay of Bengal occupies an area of 2,600,000 square kilometres (1,000,000 sq mi). A number of large rivers flow into the Bay of Bengal: the Ganges–Hooghly, the Padma, the Brahmaputra–Yamuna, the Barak–Surma–Meghna, the Irrawaddy, the Godavari, the Mahanadi, the Brahmani, the Baitarani, the Krishna and the Kaveri.