The Republic of Serbian Krajina or Serb Republic of Krajina, known as the Serbian Krajina or simply Krajina, was a self-proclaimed Serb proto-state, a territory within the newly independent Republic of Croatia, which it defied, and which was active during the Croatian War of Independence (1991–95). It was not recognized internationally. The name Krajina ("Frontier") was adopted from the historical Military Frontier of the Habsburg monarchy (Austria-Hungary), which had a substantial Serb population and existed up to the late 19th century. The RSK government waged a war for ethnic Serb independence from Croatia and unification with the Federal Republic of Yugoslavia and Republika Srpska.

The Serbs of Croatia or Croatian Serbs constitute the largest national minority in Croatia. The community is predominantly Eastern Orthodox Christian by religion, as opposed to the Croats who are Catholic.