Strandzha (Странджа, also transliterated as Strandja and Stranja; Turkish: Yıldız Dağları or Istranca) is a mountain massif in southeastern Bulgaria and the European part of Turkey, in the southeastern part of the Balkans between the plains of Thrace to the west, the lowlands near Burgas to the north and the Black Sea to the east. Its highest peak is Mahya Dağı (Махиада, Mahiada) (1031 m) in Turkey, while the highest point on Bulgarian territory is Golyamo Gradishte (710 m). The total area of the massif is approximately 10,000 km² Name of the massif is come from Istranca, which former name of Municipality of Binkılıç at Çatalca district in İstanbul province.
The mountains were the site of the Bulgarian Preobrazhenie Uprising of 1903 crushed by Ottoman troops. The current Bulgarian-Turkish border in the region was established after the Balkan Wars of 1912-1913, when the northern part of Strandzha became part of Bulgaria.
Culturally, the Bulgarian part of Strandzha is known for the specific architecture that can be observed in Malko Tarnovo, Brashlyan and most other villages, the rich folklore and distinctive rituals, such as nestinarstvo (barefoot dancing on live coals), that preserve numerous pagan elements.