The Kelantan River (Malay: Sungai Kelantan) (Jawi: سوڠاي كلنتن; Kelantanese dialect: Sunga Kelate) is a major river in Kelantan, Malaysia. Its drainage basin is about 11,900 km² in northeast Malaysia, including part of the Taman Negara, and flows northwards into the South China Sea. The rainfall over the area varies between 0 mm in the dry season (March–May) to 1,750 mm in the monsoon season (November–January). The average runoff from the area is about 500 m³/s.

The description of the river is complicated by the local naming convention: instead of using the name Kelantan river from estuary to source, the name is only used for the section from the estuary to the confluence of its two main tributaries, the Galas River and the Lebir River, near the town of Kuala Krai. The same naming convention applies to these tributaries. Thus to describe the main river from source to mouth involves four names: the River Betis (first 20 miles from the source), then the River Nenggiri, then the River Galas, and finally the Kelantan River.

The river's tributaries rise in the forested mountains in the Gua Musang region in southern Kelantan, where many Orang Asli tribes live. The area is known for its karst topography, dotted with mogotes with numerous caves beneath them. Some cave systems along the Nenggiri River, the river's left tributary, show evidence of habitation going back to 9000 years ago, such as Gua Cha near Kuala Betis.

Lower down, Malay villages dot the banks of the river which passes through one of the most densely populated floodplains in Peninsular Malaysia whose paddy fields produce around 12% of the Malaysian rice production.

The river flows past seven important towns, from south to north: Kuala Krai, Tanah Merah, Machang, Pasir Mas, Tumpat, the state capital Kota Bharu, as well as Pengkalan Chepa, Towards the estuary the river forms a delta that spans the districts of Tumpat and Kota Bharu.

The area around the actual estuary, known as Kuala Besar, is dotted with picturesque fishing villages, which are also well known for the production of batik (a local patterned material produced by waxing and dyeing cloth) for which Kelantan is famed for. The mouth of the Kelantan River is also infamous for being the site where Japanese troops first landed during their invasion of Malaya in December 1941.

The Kelantan River regularly overspills its banks during the months of November to February because of the northeast monsoon season. The estimate flood volume under the 50 year flood condition at Kusial Bridge is about 6 billion m. Severe flooding occurred in 1926 and 1967. In the 1967 floods 84% of the Kelantan population (537,000 people) were badly affected. Some 125,000 people were evacuated and 38 drowned.

More recently a telemetric flood forecasting system has been installed to give warning of high river levels. Some of the worst floods in recent years have been:

Flood impact in Kelantan

Year	Evacuees	Deaths	Damage (US$1000)
2004	10476	12	3767
2003	2228	2	1461
2001	5800	0	2227
1993	13587	0	398
1988	41059	0	?
1986	7963	0	1603
1983	33815	0	?

• List of rivers of Malaysia

• Kelantan online river level data Archived 2006-11-27 at the Wayback Machine - click Sg.Kelantan for current week's river level readings taken every hour - or click the number in the Station id column to plot a graph.
• Taman Negara Taman Negara
• [1] Kelantan

6°13′N 102°14′E / 6.217°N 102.233°E / 6.217; 102.233