The Olt River is a river in Romania. It is the longest river flowing exclusively through Romania. Its source is in the Hăşmaş Mountains of the eastern Carpathian Mountains, near the village Bălan. It flows through the Romanian counties Harghita, Covasna, Braşov, Sibiu, Vâlcea and Olt. The river was known as Alutus or Aluta in Roman antiquity. Olt County and the historical province of Oltenia are named after the river.

Sfântu Gheorghe, Râmnicu Vâlcea and Slatina are the main cities on the river Olt. The Olt flows into the Danube river near Turnu Măgurele.

The following cities are situated along the river Olt: Sfântu Gheorghe, Făgăraş, Brezoi, Călimăneşti, Râmnicu Vâlcea, Drăgăşani, Slatina.

Major tributaries to the river Olt are: Bârsa, Cibin, Cormoş, Lotru, Olteţ, Râul Negru and Topolog.