The Dulebs (Dulebes) or (more correctly) Dulebi (Russian: Дуле́бы, Ukrainian: Дуліби) were one of the tribal unions of Early East Slavs between the 6th (still questionable) and the 10th centuries. Very little is known of them, with the main source being a handful of mentions in the Primary Chronicle.
The Chronicle describes them as a tribe that formerly lived along the Bug River, in what is today eastern Ukraine. Some medieval sources also mention the Dulebs' presence in Western Volhynia, today's Czech Republic, Middle Danube, between Lake Balaton and the Mursa River (Drava).
Historians are still not sure of the exact location of the native territory of the Dulebi due to sparseness of numerous traces of the Dulebi presence, found by researchers in Central and Eastern Europe.
According to the Primary Chronicle, the Dulebi suffered greatly from the invasion of the Avars in the late 6th - early 7th century. In 907, the Dulebian unit took part in Oleg's military campaign against Czargrad. The Dulebs and their ruler were mentioned in one of the works of an Arab geographer Al-Masudi.
It appears that the Dulebi tribal union disintegrated in the 10th century, assimilated with the Volhynians and Buzhans and became part of the Kievan Rus'.