Slavonia is a region in the eastern part of the Republic of Croatia, surrounded by three rivers: the Sava in the south, the Drava in the north and Ilova in the west while on the east it borders with the Republic of Serbia. It occupies close to one quarter of the republic's territory. The largest part of Slavonija make the lowlands of Sava and Drava with the Požega valley in the north and Papuk, Psunj and Požeška gora mountains.

The region is mostly lowlands, but the eastern parts contain plains and loess plateau while its western and central parts contain hills and foothills. The climate is continental, with cold and long winters and dry and hot summers. Dominant are hornbeam, Irish oak, and pedunculate oak forests, among which the most famous is Spačva forest which is one of the biggest pedunculate oak forests in Europe - as big as the island of Krk. The largest towns are: Osijek, Slavonski Brod, Vinkovci, and Vukovar.