Banja Luka or Banjaluka is the second largest city in Bosnia and Herzegovina and the largest city of Republika Srpska, of which it is also the de facto capital. Banja Luka is the traditional centre of the densely-forested Bosanska Krajina region of northwestern Bosnia. According to the 2013 census, the city proper has a population of 138,963, while its administrative area comprises a total of 185,042 inhabitants.

The Vrbas is a major river with a length of 250 kilometres (160 mi), in western Bosnia and Herzegovina. It is a right tributary of the Sava river. The city of Banja Luka is located on the river banks.