The Una is a river in Croatia and Bosnia and Herzegovina. The river has a total length of 212 km (132 mi) and watershed area of 9,368 km2 (3,617 sq mi). The Una is a right tributary of the Sava river and the main tributaries are the Unac River, the Sana, the Klokot River and the Krušnica River. The hydrological parameters of Una are regularly monitored in Croatia at Kostajnica.
Over 170 types of medicinal herbs grow by the Una River; a rare plant called Campanula unensis, the "Una bluebell", was named after the Una river's bright turquoise and green colors. 28 kinds of fish live in this river and the biggest of which is the huchen.