Gacko is located in the southeast of Republic of Srpska (Bosnia-Herzegovina) and has the area of 736 km² with the population of about 12,000. Together with Trebinje, Ljubinje, Bileća, Berkovići and Nevesinje, Gacko makes the eastern area of Herzegovina, known as East Herzegovina.
Today’s municipality consists of 71 settlement, only one of which is urban, and remaining ones are rural.
According to a 2004 estimation, the town of Gacko has population of about 6000, while the remaining population is concentrated in rural settlements.
The Town of Gacko is not only the administrative seat but also economic, educational, cultural and demographic centre of the municipality.
The climate in the municipality of Gacko is a combination of continental and mountain type.