From August 1990 to November 1991, during the breakup of Yugoslavia, several Serb Autonomous Regions, or Districts (sing. Serbian: Српска аутономна област (САО) / Srpska autonomna oblast (SAO)) were proclaimed in the Yugoslav republics of SR Croatia and SR Bosnia and Herzegovina in light of the possible secession of the republics from the Socialist Federal Republic of Yugoslavia. These were autonomous Serb-inhabited entities that subsequently united in their respective republic to form the Republic of Serbian Krajina in Croatia and the Republika Srpska in Bosnia and Herzegovina.
The Serb Democratic Party established SAOs in Serb-inhabited territories. Between September–November 1991, six entities had been proclaimed. The Serbs set up their own parliament, having left the Bosnian parliament in October 1991. The Serb parliament proclaimed the "Serb Republic" (Republika Srpska) on 27 March 1992.