Mangroves of the Bay of Bengal is a regional ecosystem subgroup (level 4 unit of the IUCN Global Ecosystem Typology) spanning parts of South and Southeast Asia. It includes coastal areas of eastern India, Bangladesh, and northern and central Myanmar, and contains one of the largest single mangrove ecosystems in the world: the Sundarbans.Mangroves dominate along the extensive coastal waterways of the Ganges-Brahmaputra and Ayeyarwady deltas in India-Bangladesh and Myanmar, respectively. They occur on mainly coastal alluvial sediments deposited by these and other river systems. Their mapped extent in 2020 was 10,250 km2, representing 7% of the global mangrove area. The Bay of Bengal province mangroves are threatened by high population pressure and intense natural resources use, including mangrove-associated fisheries and conversion to agriculture or aquaculture. Mangrove degradation and conversion have caused serious coastal erosion. Destructive cyclones exacerbated by climate change also cause coastal erosion and damage to mangroves, while reduced freshwater flows and salinity intrusion in the Sundarbans are threatening salt-sensitive mangrove tree species like Heritiera formes. This species is classified as Endangered (EN) by IUCN, while Bruguiera hainesii and Sonneratia griffithii are Critically Endangered (CR).Today the Bay of Bengal mangroves cover ≈8% less than our broad estimation for 1970. The rate of decline has slowed since 2015 and, if the present rate persists, an overall decrease of -12% is projected over the next 50 years. However, they are expected to be resilient to even extreme sea-level rise scenarios, due to high sediment supply and vertical accretion. We estimate that 5% of the Bay of Bengal mangroves are undergoing degradation. This value could rise to 15% over a 50-year period based on decay of vegetation indexes. Overall, the Bay of Bengal mangrove ecosystem is assessed as Least Concern (LC).