Râu Sadului () is a commune in Sibiu County, Transylvania, Romania, at the foothills of the Cindrel Mountains, south of the county capital Sibiu, in the Mărginimea Sibiului ethnographical area. It is composed of a single village, Râu Sadului.
The commune lies on the banks of the river Sadu, at an altitude of . It is located in the southern part of the county, on the border with Vâlcea County.
At the 2011 census, the commune had 571 inhabitants, of which 96.85% were ethnic Romanians. At the 2021 census, the Râu Sadului had a population of 514; of those, 87.16% were Romanians.
References