Rangamati District is an administrative region of Chittagong Division in the southeastern part of Bangladesh. It is a hilly district. It is the largest district of Bangladesh.
Karnaphuli is the main river of Rangamati district. The river originates in the Lusai Hills of India and enters the region through the estuary of the Thega River along the northeastern border of Rangamati. The tributaries of the Karnaphuli River are Kachalong, Maini, Chengi, Thega, Salak, Raingkhyong. Besides, this district has the largest Kaptai lake in Bangladesh. Although these tributaries have sufficient flow during the rainy season, the amount of water including navigability is not nearly there during the dry season.