The Olt is a river in Romania. It is 615 km (382 mi) long, and its basin area is 24,050 km2 (9,290 sq mi). It is the longest river flowing exclusively through Romania. Its average discharge at the mouth is 174 m3/s (6,100 cu ft/s). Its source is in the Hășmaș Mountains of the eastern Carpathian Mountains, near Bălan, rising close to the headwaters of the river Mureș. It flows through the Romanian counties Harghita, Covasna, Brașov, 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.
Bistrița is a right tributary of the river Olt in Romania. It discharges into the Olt near Băbeni. It starts in the Căpățânii Mountains forming one of the narrowest gorges in Romania and some beautiful caves. It flows through the villages Bistrița, Costești, Bălțățeni, Tomșani, Foleștii de Jos and Frâncești. Its length is 50 km (31 mi) and its basin size is 355 km2 (137 sq mi).
The Aita is a right tributary of the river Olt in Romania. It discharges into the Olt in Aita Mare. Its length is 25 km (16 mi) and its basin size is 132 km2 (51 sq mi).
The Lotru is a right tributary of the river Olt in Romania. Its source is in the Parâng Mountains. It feeds the reservoirs Vidra, Malaia and Brădișor. It flows into the Olt in Golotreni, near the town Brezoi. It passes through the communes Voineasa, Malaia, and Brezoi. Its length is 83 km (52 mi) and its basin size is 990 km2 (380 sq mi).
The Avrig is a left tributary of the river Olt in Romania. It discharges into the Olt in the town Avrig. The upper reach of the river is also known as Râul Mare. Its source is the Avrig Lake in the Făgăraș Mountains. Its length is 24 km (15 mi) and its basin size is 66 km2 (25 sq mi).
The Vâlcele is a right tributary of the river Olt in Romania. It discharges into the Olt in Araci. Its length is 11 km (6.8 mi) and its basin size is 32 km2 (12 sq mi).
The Ghimbășel is a left tributary of the river Bârsa in Romania. Its source is in the northern part of the Bucegi Mountains. Originally it discharged directly into the Olt, but much of its flow has been diverted into the Bârsa, another tributary of the Olt, near Colonia Bod. Its length is 67 km (42 mi) and its basin size is 533 km2 (206 sq mi). The former lower course of the Ghimbășel, downstream of this diversion, still exists and is used for the discharge of local inflows. It flows into the Olt north of Bod. Its length is 6 km (3.7 mi) and its basin size is 8 km2 (3.1 sq mi).
The Homorod or Ciucaș is a left tributary of the river Olt in Romania. It discharges into the Olt in Feldioara. Its length is 40 km (25 mi) and its basin size is 322 km2 (124 sq mi). Near the village of Satu Nou the river divides into two branches, the main branch keeping the name of Homorod, while the secondary branch is named Homorodul Vechi. The two branches join again upstream of Feldioara.
The Lotrioara is a right tributary of the river Olt in Romania. Its source is in the Lotru Mountains. It discharges into the Olt in Lazaret. Its length is 25 km (16 mi) and its basin size is 120 km2 (46 sq mi).
The Olteț is a right tributary of the river Olt in Romania. It discharges into the Olt in Fălcoiu. Its total length is 185 km (115 mi), and its drainage basin area is 2,663 km2 (1,028 sq mi).
The Valea Crișului is a right tributary of the river Olt in Romania. It flows into the Olt in Ghidfalău. Its length is 16 km (9.9 mi) and its basin size is 33 km2 (13 sq mi).
The Vad is a right tributary of the river Olt in Romania. It discharges into the Olt in Lazaret. Its length is 12 km (7.5 mi) and its basin size is 46 km2 (18 sq mi).
The Râul Negru is a left tributary of the river Olt in Romania. It discharges into the Olt in Lunca Câlnicului. It flows through the villages Lemnia, Lunga, Catalina, Hătuica, Surcea, Telechia, Bita, Reci, Sântionlunca, Ozun, Băcel, Chichiș and Lunca Câlnicului. Its length is 88 km (55 mi) and its basin size is 2,349 km2 (907 sq mi).
The Șercaia is a left tributary of the river Olt in Romania. It discharges into the Olt in Hălmeag. Its length is 46 km (29 mi) and its basin size is 350 km2 (140 sq mi). The upper reach of the river, upstream of the confluence with the Holbav is also known as Valea Poiana Mărului. The middle reach of the river, from the junction with the Holbav to the confluence with the Scurta is also known as the Șinca.
The Bârsa is a left tributary of the river Olt in Romania. It discharges into the Olt near Feldioara. Its source is in the Făgăraș Mountains. As several tributaries also have the name Bârsa, in order to differentiate them, the main course of the river is frequently referred to as Bârsa Mare. The river Ghimbășel, formerly a direct tributary of the Olt, was redirected towards the Bârsa. Its length is 73 km (45 mi) and its basin size is 937 km2 (362 sq mi).
The Sebeș is a left tributary of the river Olt in Romania. It discharges into the Olt east of Făgăraș. Its source is in the Făgăraș Mountains. Its length is 38 km (24 mi) and its basin size is 94 km2 (36 sq mi).
The Băiaș is a left tributary of the river Olt in Romania. It discharges into the Olt in Copăceni. Its length is 19 km (12 mi) and its basin size is 87 km2 (34 sq mi).
The Baraolt is a right tributary of the river Olt in Romania. It discharges into the Olt in Căpeni. Its length is 40 km (25 mi) and its basin size is 221 km2 (85 sq mi).
The Călinești is a right tributary of the river Olt in Romania. It discharges into the Olt in the village Călinești. Its length is 18 km (11 mi) and its basin size is 43 km2 (17 sq mi).
The Geamărtălui is a right tributary of the river Olteț in Romania. It discharges into the Olteț in the town Balș. The following towns and villages are situated along the river, from source to mouth: Velești, Balota de Sus, Balota de Jos, Bușteni, Gaia, Murgași, Picăturile, Plopșorelu, Tabaci, Vulpeni, Gropșani, Găvănești, Dâmburile, Baldovinești and Balș. Its length is 63 km (39 mi) and its basin size is 421 km2 (163 sq mi).
