Ključ (Serbian Cyrillic: Кључ) is a village in the municipality of Gacko, Republika Srpska, Bosnia and Herzegovina.

Ključ, and wider Bosnia was annexed by Austria 1878, when Austrian troops entered this area, however, the region had been under habsburg spare of influence for some time.

Following World War I, Bosnia and Herzegovina joined the South Slav Kingdom of Serbs, Croats and Slovenes (soon renamed Yugoslavia).Once the Kingdom of Yugoslavia was conquered by German forces in World War II, all of Bosnia was ceded to the Nazi puppet regime, the Independent State of Croatia (NDH) led by the Ustaše.

A second round followed on 25 November, resulting in a national assembly where communist power was replaced by a coalition of three ethnically-based parties.

[4] A declaration of the sovereignty of Bosnia and Herzegovina on 15 October 1991 was followed by a referendum for independence on 29 February and 1 March 1992, which was boycotted by the great majority of Serbs.