Trebinje (Serbian Cyrillic Требиње, German earlier Trebing) is a town in the southeast corner of Bosnia and Herzegovina, near the border with Montenegro and Croatia. It belongs to Republika Srpska and is located in the historic region of Herzegovina on the river Trebišnjica about 25 km from the Adriatic Sea, which they regarded as an outpost to the Adriatic Sea. It is to Mostar, the second largest city in the region.