The SAO of Herzegovina (Serbian: Српска аутономна област Херцеговина, Srpska autonomna oblast Hercegovina ) was a self-proclaimed Serbian Autonomous Oblast within today's Bosnia and Herzegovina. It was proclaimed by the Assembly of the Association of Municipalities of Bosnian Krajina in 1991 and was subsequently included into Republika Srpska. SAO Herzegovina was located in the geographical region of Herzegovina. It was also known as SAO Eastern Herzegovina (SAO Istočna Hercegovina / САО Источна Херцеговина).
SAO Herzegovina was formed from the Association of Municipalities (a government in SFRY) known as Assembly of the Communities of East Herzegovina, which was formed on 27 May 1991. The SAO East and Old Herzegovina was established on September 12, 1991. It consisted of East Herzegovina which had a Serb ethnic majority. Its capital was Trebinje.
Herzegovina (/ˌhɛərtsᵻˈɡoʊvᵻnə/ or /ˌhɜːrtsəɡoʊˈviːnə/;Bosnian, Croatian and Serbian: Hercegovina, Херцеговина, [xɛ̌rtsɛɡov̞ina]) is the southern region of Bosnia and Herzegovina. While there is no official border distinguishing it from the Bosnian region, it is generally accepted that the borders of the region are Croatia to the southwest, Montenegro to the east, Mount Maglić to the northeast, and Mount Ivan to the north. Measurements of the area range from 11,419 km2 (4,409 sq mi), or around 22% of the total area of the present-day country, to 12,276 km2 (4,740 sq mi), around 24% of the country.
The name Herzegovina means "duke's land", referring to the medieval duchy of Stjepan Vukčić Kosača who took title "Herzeg of Saint Sava". Herceg is derived from the German title Herzog.
The terrain of Herzegovina is mostly hilly karst with high mountains in the north such as Čvrsnica and Prenj, except for the central valley of the river Neretva River. The largest city is Mostar, in the center of the region. Other larger towns include Trebinje, Stolac, Široki Brijeg, Konjic, and Čapljina. Borders between Bosnia and Herzegovina are unclear and often disputed.