Kumu River is a river in Riau province, central-eastern Sumatra, Indonesia, about 1,100 km northwest of the capital Jakarta. It is a tributary of the Rokan River.
The river flows in the central area of Sumatra which has a predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification). The annual average temperature in the area is 23 ðC. The warmest month is March, when the average temperature is around 24 ðC, and the coldest is January, at 22 ðC. The average annual rainfall is 3766 mm. The wettest month is November, with an average of 336 mm rainfall, and the driest is July, with 113 mm rainfall.