The Triballi were an ancient Thracian people whose earliest home was near the junction of the Angrus and Brongus (the East and West Morava), and included towards the south the Triballian plain, which corresponds to the plain of Kosovo in Serbia.
In 424 BC they were attacked by Sitalces, king of the Odrysae, who was defeated and lost his life in the engagement. On the other hand, they were overcome by the Autariatae, an Illyrian tribe; the date of this event is uncertain.
In 376 BC, a large band of Triballi crossed Mount Haemus and advanced as far as Abdera; they were preparing to besiege the city, when Chabrias appeared off the coast with the Athenian fleet and compelled them to retire.
In 339 BC, when Philip II of Macedon was returning from his expedition against the Scythians, the Triballi refused to allow him to pass the Haemus unless they received a share of the booty. Hostilities took place, in which Philip was defeated and nearly lost his life, but the Triballi appear to have been subsequently subdued by him.
After the death of Philip, the Triballi having taken up arms again, Alexander the Great in 334 BC crossed the Haemus and drove them to the junction of the Lyginus with the Danube. Their king Syrmus took refuge in Peuce (Peuk, an island in the Danube), whither Alexander was unable to follow him.
The punishment inflicted by him upon the Getae, however, induced the Triballi to sue for peace. About 280 BC a host of Gauls under Cerethrius defeated the Getae and Triballi. Nevertheless, the latter for some fifty years (135 BC-84 BC) caused trouble to the Roman governors of Macedonia.
In the time of Ptolemy their territory is limited to the district between the Ciabrus (Tzibritza) and Utus (Vid), in the modern Bulgaria, their chief town being Oescus.
Under Tiberius mention is made of Treballia in Moesia, and the Emperor Maximin (235-237) had been commander of a squadron of Triballi. The name occurs for the last time during the reign of Diocletian, who dates a letter from Triballis.
The Triballi were often described as a wild and warlike people (Isocrates), and in Aristophanes, a Triballian is introduced as a specimen of an uncivilized barbarian.
