Koula is a mountain range on the borderline of the neighboring countries Greece and Bulgaria; it is the natural border between the Region of Eastern Macedonia-Thrace and the Region of Macedonia, forming the backbone of the regional units of Xanthi and Drama. Koula is part of Central Rodopi. It consists of two mountain ranges, namely, Mount Haidou (also known as Erymanthos) and Mount Stamna.
The rivers Arda and Kossynthos spring from the mountain range of Koula.