The Otava is a river in the Czech Republic, a left tributary of the Vltava River. It flows through the Plzeň and South Bohemian regions. It is formed by the confluence of the Vydra and Křemelná rivers. Together with the Vydra, which is its main source, the Otava is 134.8 km (83.8 mi) long, which makes it the 13th longest river in the country. Without the Vydra, it is 111.7 km (69.4 mi) long.