The Buna (Буна) is a short river in Bosnia and Herzegovina; it is a left-bank tributary of the Neretva. Its source, Vrelo Bune (Buna Spring), is a strong karstic spring located near the village of Blagaj, southeast of Mostar. Vrelo Bune is one of the strongest springs in Europe and has extremely cold water. The Buna flows west for approximately 9 km, starts at Blagaj and, meandering through the villages of Blagaj, Kosor, Malo Polje and Hodbina, joins the Neretva near the settlement Buna. The site of confluence is called Buna Canals. The Bunica river is the main left-bank tributary of the Buna. The Buna is major habitat for an endemic trout species known under its vernacular name as Softmouth trout.