Blagaj is a village-town (kasaba) in the south-eastern region of the Mostar basin, in the Herzegovina-Neretva Canton of Bosnia and Herzegovina. It stands at the edge of Bisce plain and is one of the most valuable mixed urban and rural structures in Bosnia and Herzegovina, distinguished from other similar structures in its urban layout. Blagaj was most likely named for its mild weather patterns since "blaga" in Bosnian means "mild". Blagaj is situated at the spring of the Buna river and a historical tekke (tekija or Dervish monastery). The Blagaj Tekija was built around 1520, with elements of Ottoman architecture and Mediterranean style and is considered a national monument.
The source of the Buna river (Vrelo Bune) is a strong karstic spring. The Buna flows west for approximately 9 kilometres and joins the Neretva near the village Buna.
The historic site of the Old Blagaj Fort (Stjepan grad), on the hill above Blagaj, was the seat of Herzegovinian nobleman, Stjepan Vukcic, and the birthplace of Bosnian queen Katarina Kosaca-Kotromanic