The Pirin Mountains (Bulgarian: Пирин) are a mountain range in southwestern Bulgaria, with Vihren at an altitude of 2,914 m being the highest peak. The mountain is named after Perun (Bulgarian: Перун), the highest god of the Slavic pantheon and the god of thunder and lightning. In the Antiquity the range was called Perinthos by the Thracians, meaning "Rocky Mountain".
The range extends about 80 km from the north-west to the south-east and is about 40 km wide, spanning a territory of 2,585 km2 (998 sq mi). To the north Pirin is separated from Bulgaria's highest mountain range, the Rila Mountains, by the Predel saddle, while to the south it reaches the Slavyanka Mountains. To the west is located the valley of the river Struma and to the east the valley of the river Mesta separates it from the Rhodope Mountains. Pirin is dotted with more than a hundred glacial lakes and is also the home of Europe's southernmost glaciers, Snezhnika and Banski Suhodol.
The northern part of the range, which is also the highest one, is protected by the Pirin National Park, declared a UNESCO World Heritage Site in 1983. Pirin is noted for its rich flora and fauna, as well as for the presence of a number of relict species. Much of the area is forested, with some of the best preserved conifer woods in Bulgaria, holding important populations of the Balkan endemic species Macedonian pine, Bosnian pine and Bulgarian fir. Animals include many species of high conservation value, such as brown bear, gray wolf, wildcat, European pine marten, wild boar, red deer, roe deer, chamois, etc.
The combination of favourable natural conditions and varied historical heritage contribute makes Pirin an important tourist destination. The town of Bansko, situated on the north-eastern slopes of the mountain, has grown to be the primary ski and winter sports centre in the Balkans. A number of settlements at the foothills of Pirin have mineral spring and are spa resorts — Banya, Dobrinishte, Gotse Delchev, Sandanski, etc. Melnik at the south-western foothills of the mountain is Bulgaria's smallest town and is an architectural reserve. Within a few kilometres from the town are the Melnik Rock Pyramids and the Rozhen Monastery.