Feni River rises from the hill ranges of the Indian state of tripura at 23°20'N and 91°47'E, flows southwest marking the boundary with the chittagong hill tracts, then flows west, separating Tripura from chittagong up to Aliganj and then emerges out of the hills and passes through the plains dividing Chittagong from noakhali before falling into the bay of bengal at 22°50'N and 91°27'E. This river belongs to Bangladesh as it used to form the demarcation line between Chittagong, Noakhali and Tripura State of India. But since 1960, India is using the river, claiming their right up to the midstream.
The river is 116 km long from the source to the Bay of Bengal and 80.5 km of it up to Ramgarh is navigable throughout the year by small boats. During monsoon rains it remains full of water but with every heavy shower in its catchment area it becomes furious with rapid currents and whirling eddies at sharp turns. The muhuri from Noakhali district, also called little feni, falls into it near its mouth but it has no important affluent from Chittagong district. The river is gradually silting up due to reckless extraction of timber tree from the hill slopes and consequent heavy erosion of the hills. [Sifatul Quader Chowdhury]
See map in chittagong region river system.