Võnnu (German: Wenden) is a small borough (Estonian: alevik) in Tartu County, in Kastre Parish, Estonia.

It is located about 21 km (13 mi) southeast of the city of Tartu.

Võnnu was attested in historical sources as Wenden in 1582, Wendehof in 1630, Wendo Kÿlla in 1638, and Wendohof in 1740.

The linguist Julius Mägiste compared the name to Finnish vieno 'gentle, quiet (also referring to running water)', relating it to a swampy place.

This view was also endorsed by the folklorist Matthias Johann Eisen.