Deli River (Indonesian: Sungai Deli) is a river located in Sumatra, Indonesia, and courses through Medan before discharging to the Strait of Malacca near the port city of Belawan.

The Deli Sultanate was founded on the delta of the river around 1640,[1] and later around the 19th century, this river acted as an artery of trade for the sultanate to other areas.

With an area of 48 162 hectares, length of 73 kilometers (km), and a width of 5.58 m, Deli watershed should have at least 140 hectares, or 30 percent of the watershed.

The river flows in the northeastern area of Sumatra with predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).

The warmest month is January, when the average temperature is around 26 °C, and the coldest is December, at 22 °C.