The Bosna (Serbian Cyrillic: Босна, pronounced [bɔ̂sna]) is the third longest river in Bosnia and Herzegovina, and is considered one of the country's three major internal rivers, along with the Neretva and the Vrbas. The other three major rivers of Bosnia and Herzegovina are the Una, to the northwest; the Sava, to the north, and the Drina, to the east. This river is the namesake of Bosnia. The river Bosna flows for 282 kilometers (175 mi).

The river is possibly mentioned for the first time during the 1st century AD by Roman historian Marcus Velleius Paterculus under the name Bathinus flumen. Another basic source that is associated with the hydronym Bathinus is the Salonitan inscription of the governor of Dalmatia, Publius Cornelius Dolabella, where it is said that the Bathinum river divides the Breuci from the Osseriates. And also by the name of Basante. According to philologist Anton Mayer the name Bosna could be derived from Illyrian Bass-an-as(-ā) which would be a diversion of the Proto-Indo-European root bʰegʷ, meaning "the running water".