Bačka (Бачка, bâːtʃkaː) or Bácska (ˈbaːtʃkɒ) is a geographical and historical area within the Pannonian Plain bordered by the river Danube to the west and south, and by the river Tisza to the east. It is divided between Serbia and Hungary. Most of the area is located within the Vojvodina region in Serbia and Novi Sad, the capital of Vojvodina, lies on the border between Bačka and Syrmia. The smaller northern part of the geographical area is located within Bács-Kiskun County in Hungary.
According to Serbian historians, Bačka is a typical Slavic name form, created from "Bač" (name of historical town in Bačka) and suffix "ka" (which designates "the land that belongs to Bač").
The name of "Bač" (Bács) town is of uncertain origin and its existence was recorded among Vlachs, Slavs and Hungarians in the Middle Ages. The origin of the name could be Paleo-Balkanic, Romanian, Slavic, or Old Turkic.
According to Hungarian historians, the denominator of the landscape may have been the first bailiff of Bač (Bács) castle, and the name which can be rendered probably Old Turkic baya derives from a dignity name.
In the 17th and 18th century, due to the large number of Serbs who lived in Bačka, this region was called »Raczorszag« (Hungarian for "the Serb country"). Sometimes, the Hungarians used name Délvidék ("the southern or lower country") for a wider imprecisely defined geographical area, which, according to 19th century view also included Bačka. However, according to other Hungarian sources, Bačka was rather seen as part of Alföld.
Through history, Bačka has been a part of Dacia, the Kingdom of the Iazyges, the Hun Empire, the Gepid Kingdom, the Avar Khanate, the First Bulgarian Empire, the Great Moravia, the Kingdom of Hungary, the Serb realm of Jovan Nenad, the Ottoman Empire, the Habsburg monarchy, the Austrian Empire, Austria-Hungary, the Kingdom of Serbia, the Kingdom of Serbs, Croats and Slovenes, the Kingdom of Yugoslavia, the Socialist Federal Republic of Yugoslavia, the Federal Republic of Yugoslavia, Serbia and Montenegro, and since 2006, it has been part of an independent Republic of Serbia.