Trebinje is the southernmost municipality and city in Bosnia and Herzegovina. Located in East Herzegovina, it is part of the Republika Srpska entity, and its population numbers 31,433. The city lies in the Trebišnjica river valley, at the foot of Leotar, some 30 km by road from Dubrovnik on the Adriatic coast.

There are several mills along the river, as well as several bridges, including three in the city of Trebinje itself, as well as a historic Ottoman Arslanagic bridge nearby. The river is heavily exploited for hydro-electric energy.

After it passes through the Popovo Polje area southwest of the city, the river - which always floods in the winter - naturally runs underground to the Adriatic, near Dubrovnik. Trebinje is known as "the city of the sun and platan trees", and it is said to be one of the most beautiful cities in Bosnia and Herzegovina. The city is economic and cultural center of the region of Eastern Herzegovina.