The Lower Gangetic plains moist deciduous forests is a tropical moist broadleaf forest ecoregion of Bangladesh and eastern India. The ecoregion covers an area of 254,100 square kilometers (98,100 sq mi), covering most of Bangladesh and the Indian states of West Bengal, Bihar, and Tripura, and extending into adjacent portions of Assam, Uttar Pradesh, and Orissa states.
The Lower Gangetic plains moist deciduous forests extends across the alluvial plain of the lower Ganges and Brahmaputra rivers, which form the world's largest river delta. The ecoregion is currently one of the most densely-populated regions on earth, and the forests have largely been replaced with intensive agriculture.
The ecoregion is bounded on the east and northeast by montane tropical rain forests; the Mizoram-Manipur-Kachin rain forests lie in the Chin Hills and Chittagong Hills to the east, and the Meghalaya subtropical forests lie in the Khasi Hills and Garo Hills to the northeast. To the north, the ecoregion extends to the base of the Himalayas, where it is bounded by the Terai-Duar savanna and grasslands. The upper portion of the Brahmaputra valley in Assam is home to the humid lowland Brahmaputra Valley semi-evergreen forests. To the northwest, the forests are bounded by the Upper Gangetic plains moist deciduous forests, and the dry Chota Nagpur dry deciduous forests lie on the Chota Nagpur Plateau to the northwest. The Sundarbans freshwater swamp forests and Sundarbans mangroves ecoregions lie in the swampy, semi-brackish and brackish southern reaches of the Ganges-Brahmaputra Delta bordering the Bay of Bengal.