The Bay of Bengal is a triangular embayment of the northeastern Indian Ocean, spanning roughly 2.17 million square kilometres, making it the largest bay on Earth. It is bounded by India and Sri Lanka to the west, Bangladesh to the north, Myanmar and the Andaman–Nicobar arc to the east, and opens southward toward the Indian Ocean proper, conventionally delimited along a line from Sangaman Kanda (Sri Lanka) to the northern tip of Sumatra. Several of South Asia's great rivers — the Ganga–Brahmaputra–Meghna system, the Mahanadi, Godavari, Krishna and Cauvery, and Myanmar's Irrawaddy — discharge into it, depositing the Bengal Fan, the world's largest submarine fan, which extends some 3,000 km southward. This freshwater influx produces a strongly stratified, low-salinity surface layer that governs the Bay's distinctive monsoon dynamics.
Hydrographically the Bay is the cradle of the South Asian summer monsoon and a principal genesis basin for tropical cyclones, which form chiefly during the pre-monsoon (April–May) and post-monsoon (October–November) seasons. Funnel-shaped coastlines at the head of the Bay amplify storm surges, making the Bangladesh and Odisha coasts among the most cyclone-vulnerable on the planet; the 1970 Bhola cyclone killed an estimated 300,000–500,000 people, and the 1999 Odisha super-cyclone and Cyclone Sidr (2007) inflicted catastrophic losses. The Bay is rich in hydrocarbons (notably the Krishna–Godavari basin and Myanmar's offshore gas) and fisheries, and carries dense shipping through ports including Chennai, Visakhapatnam, Kolkata, Paradip, Chattogram and Yangon.
Maritime boundaries in the Bay were a major arena of legal settlement under the UN Convention on the Law of the Sea (UNCLOS, 1982). In Bangladesh v. Myanmar (2012) the International Tribunal for the Law of the Sea (ITLOS) delimited their boundary, recognising Bangladesh's entitlement to a substantial continental shelf, and the Bangladesh v. India arbitration (2014) under Annex VII of UNCLOS resolved their dispute, awarding Bangladesh about four-fifths of the contested 25,602 sq km. Regionally, the Bay anchors BIMSTEC (the Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation, founded 1997), which by 2026 had assumed growing salience in India's "Act East" policy and as a maritime-security node amid Indo-Pacific great-power competition, including expanding Chinese activity around Myanmar's Kyaukpyu and Sri Lanka's Hambantota.
For the examinations, the Bay of Bengal recurs across multiple papers. In UPSC Geography it tests physical features — the Bengal Fan, monsoon onset, cyclone genesis and coastal geomorphology — and in International Relations the ITLOS/UNCLOS delimitations, BIMSTEC and Indo-Pacific strategy. For the BCS "Bangladesh in the World" paper it is central: candidates must know the 2012 and 2014 verdicts, the blue-economy potential, the Ganga–Brahmaputra delta, and Bangladesh's cyclone-preparedness regime. Typical question angles ask candidates to relate the Bay's hydrography to monsoon mechanics, to summarise the legal basis of maritime boundary settlements, or to assess BIMSTEC's role in regional cooperation. Mastery requires linking the physical geography to the strategic and legal frameworks that make the Bay a contemporary geopolitical fulcrum.
Example
In 2014, an Annex VII UNCLOS arbitral tribunal at The Hague settled the Bangladesh–India maritime boundary, awarding Bangladesh roughly four-fifths of the disputed 25,602 sq km in the Bay of Bengal.
Frequently asked questions
The Bangladesh–Myanmar boundary was delimited by ITLOS in 2012, and the Bangladesh–India dispute by an Annex VII UNCLOS arbitral tribunal in 2014. Both applied the equidistance/relevant-circumstances method and recognised Bangladesh's continental-shelf entitlement, awarding it the larger contested area.