| Sanzu River | |
| Pushpin Map: | Burundi |
| Subdivision Type1: | Country |
| Subdivision Name1: | Burundi |
| Mouth Location: | Nyabaha River |
The Sanzu River (fr|Rivière Sanzu) is a river in Burundi, a right tributary of the Nyabaha River.
The Sanzu River forms in the east of Ruyigi Province to the southwest of Kigamba and northwest of the city of Ruyigi.It is formed where the Rusabagi River from the northwest joins the Rutimbura River from the southeast.It flows west to join the Nyakijanda River, which flows from the south. The combined stream is the Nyabaha River, which flows northwest to join the Ruvubu River.The Sanzu flows through the Commune of Ruyigi and the Commune of Butaganzwa.
The surroundings of the Sanzu river are a mosaic of farmland and natural vegetation.The area is quite densely populated, with 111 inhabitants per square kilometer as of 2016.The average annual temperature in the area is .The warmest month is September, when the average temperature is, and the coldest is April, with .Average annual rainfall is . The rainiest month is December, with an average of of precipitation, and the driest is July, with of precipitation.
There is an old hydroelectric dam owned by Regideso on the Sanzu River on the Ruyigi-Kayongozi road, about from Ruyigi.The power plant ceased to function in 2000, and the canal that carried water to the plant became clogged due to lack of maintenance.This has caused flooding to several rice fields along a stretch. In April 2023 one of the pipes broke, causing further damage.
In May 2023 torrential rain caused the flooding of marshes beside the Sanzu River in Ruhwago colline, Commune of Ruyigi.Beans, corn, potatoes, sweet potatoes and other crops were washed away about three weeks before they were to be harvested.