The Bessi were an independent Thracian tribe who lived in a territory ranging from Moesia to Mount Rhodope in southern Thrace, but are often mentioned as dwelling about Haemus, the mountain range that separates Moesia from Thrace. Herodotus described them as a sort of priestly-caste among the Satrae, the Bessi being interpreters of the prophetic utterances given by a priestess in an oracular shrine of Dionysus located on a mountain-top.

In Strabo, however, the Bessi are described as the fiercest of the independent Thracian tribes, dwelling on and around the Haemus range, and possessing the greater part of the area around that mountain chain.

Towards the end of the 4th century ad, Niketas the Bishop of Dacia brought the gospel to "those mountain wolves", the Bessi. Reportedly his mission was successful, and the worship of Dionysus and other Thracian gods was eventually replaced by Christianity.

In the 11th century Strategikon text, Cecaumenos the Byzantine described the Vlachs (Romanians and Aromanians) as being descendants of the Daci and of the Bessi.

See also: Dii. Satrae. Haemus Mons.