The Bay of Bengal, the largest bay in the world,

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

The Bay of Bengal occupies an area of 2,172,000 square kilometres (839,000 sq mi). A number of large rivers – the Ganges and its tributaries such as the Padma and Hooghly, the Brahmaputra and its tributaries such as the Jamuna and Meghna, other rivers such as the Irrawaddy River, Godavari, Mahanadi, Krishna and Kaveri flow into the Bay of Bengal. Among the important ports are Chennai, Chittagong, Kolkata, Mongla, Paradip, Tuticorin, Visakhapatnam and Yangon.

Many major rivers of the Indian subcontinent flow west to east before draining into the Bay of Bengal. The Ganges is the northernmost of theses. Its main channel enters and flows through Bangladesh, where it is known as the Padma River, before joining the Meghna River. However, the Brahmaputra River flows from east to west in Assam before turning south and entering Bangladesh where it is called the Jamuna River. This joins the Padma whereupon the Padma joins the Meghna River that finally drains into Bay of Bengal. The Sundarbans mangrove forest at the delta of the Ganges, Brahmaputra and Meghna rivers lies partly in West Bengal and partly in Bangladesh. The Brahmaputra at 2,948 km (1,832 mi) is the 28th longest River in the world. It originates in Tibet. The Hooghly River, another channel of the Ganga that flows through Calcutta drains into Bay of Bengal in India itself.

The Ganga–Brahmaputra rivers deposits nearly 1000 million tons of sediment per year. The sediment from these two rivers forms the Bengal Delta and the submarine fan, a vast structure that extends from Bangladesh to south of the Equator, is up to 16.5 kilometres (10.3 mi) thick, and contains at least 1,130 trillion tonnes of sediment, which has accumulated over the last 17 million years at an average rate of 665 million tons per annum. The Bay of Bengal used to be deeper than the Mariana Trench, the present deepest ocean point. The fan has buried organic carbon at a rate of nearly 1.1 trillion mol/yr since the early Miocene period. The two rivers currently contribute nearly 8% of the total organic carbon (TOC) deposited in the world's oceans. Due to high TOC accumulation in the deep sea bed of the Bay of Bengal, the area is rich in oil and natural gas and gas hydrate reserves. Bangladesh can reclaim land substantially and economically from the sea area by constructing sea dikes, bunds, causeways and by trapping the sediment from its rivers.

Further south of Bengal, the Mahanadi, Godavari, Krishna and Kaveri Rivers are the major rivers that flow from west to east in the Indian subcontinent and drain into the Bay of Bengal. Many small rivers also drain directly into the Bay of Bengal; the shortest of them is the Cooum River at 64 km (40 mi).

The Irrawaddy (or Ayeyarwady) River in Myanmar flows into the Andaman Sea of the Bay of Bengal and once had thick mangrove forest of its own.

The Bay of Bengal is strategically crucial for India since it is a natural extension of its sphere of influence. Secondly because of the presence of outlying islands, namely Andaman islands and Nicobar islands and most importantly several major ports such as Kolkata, Chennai, Visakhapatnam, and Tuticorin along its coast with the Bay of Bengal.

China has recently made some efforts to project influence into the region through tie-ups with Myanmar and Bangladesh.The United States has held several major exercises with Bangladesh, India, Malaysia, Singapore and Thailand. The largest ever wargame in Bay of Bengal, known as Malabar 2007, was held in 2007 and naval warships from US, Singapore, Japan and Australia took part in it. India, was also a participant. Large deposits of natural gas also incited a serious up for grabs urgency by India. Disputes over rights of some oil and gas blocks have caused brief diplomatic spats between Myanmar and India with Bangladesh.

The disputed maritime boundary between Bangladesh and Myanmar has twice resulted in military tensions, in 2008 and 2009. Bangladesh is currently pursuing a settlement with Myanmar and India to the boundary dispute through the International Tribunal on the Law of the Sea.

It has been argued that the conceptual division of the Bay of Bengal region between South Asia and Southeast Asia may no longer be appropriate and that the rise of India as a major power may lead to a new mental mapping of the Bay of Bengal as a coherent strategic region.