The Kwisa [ˈkfʲisa] (German: Queis, Upper Sorbian: Hwizdź, pronounced [ˈhwʲistʃ]) is a river in south-western Poland, a left tributary of the Bóbr, which itself is a left tributary of the Oder river.
It rises in the Jizera Mountains, part of the Western Sudetes range, where it runs along the border with the Czech Republic. At the slope of the Smrk massif it turns northwards, flowing along the towns of Świeradów-Zdrój, Mirsk, Gryfów Śląski, Leśna, where it is dammed at the Lake Leśnia reservoir, to Lubań, Nowogrodziec and Kliczków. It finally joins the Bóbr river approximately 2 kilometres (1.2 mi) north-west of Małomice and 5 km (3.1 mi) south-east of Żagań. For most of its length it is in Lower Silesian Voivodeship, but it also flows through Lubusz Voivodeship for several kilometres before reaching its mouth.