Sungai Kelantan is the longest and most important river in Kelantan. The state capital, Kota Bharu, lies on its eastern bank. The name Sungai Kelantan begins at the confluence of Sungai Galas with Sungai Lebir, near the town of Kuala Krai. Above that confluence, the river is called Sungai Galas, Sungai Nenggiri and for its first twenty miles, Sungai Betis.
In addition to Kota Bharu and Kuala Krai, Sungai Kelantan also flows through the town of Pasir Mas. Along with all its tributaries, it has a catchment area totalling 11,900 square kilometers. As it reaches the South China Sea, it fans out into a wide delta.