Southern Bulgaria

Besides the Balkan Mountains, Southern Bulgaria borders Serbia to the west, North Macedonia to the southwest, Greece to the south, Turkey to the southeast and the Bulgarian Black Sea Coast to the east.

Geographically, the terrain in Southern Bulgaria is much more varied than that of the north, with the Upper Thracian Plain stretching in the east, while the south and west are dominated by some of Bulgaria's highest mountains such as Rila, Pirin and the Rhodopes, as well as smaller and/or lower mountains and valleys in the west, such as Vitosha, Belasitsa, Osogovo, the Sofia Valley, the Sub-Balkan valleys and the Kraishte region.

The Bulgarian South also has a number of often unclearly defined or overlapping sub-regions, particularly in the west and southwest, such as Chech, Shop region, Kraishte, Burel, Visok, Zabardie, Znepole, Graovo, Osogoviya, Piyanets, Podgorie, Razlog, Rupchos, Tamrash, etc.

In Antiquity, the Jireček Line divided Latin (in the north) and Ancient Greek (in the south) language influence in the Balkans, with Northern Bulgaria to the north of it and Southern Bulgaria to the south.

Pirin Macedonia became part of Bulgaria after the Treaty of Bucharest of 1913, and the only Bulgarian gains by the otherwise catastrophic post-World War I Treaty of Neuilly-sur-Seine of 1919 were two small strips of land in southern Sakar.