The Liburnians (or Liburni, Greek: Λιβυρνοί) were an ancient tribe, possibly Illyrian, inhabiting the district called Liburnia, a coastal region of the northeastern Adriatic between the rivers Arsia (Raša) and Titius (Krka) in what is now Croatia.
The first account of the Liburni comes from Periplus or Coastal passage, an ancient Greek text of the mid 4th century BC.
The fall of Liburnian domination in the Adriatic Sea and their final retreat to their ethnic region (Liburnia) were caused by the military and political activities of Dionysius the Elder of Syracuse (406 – 367 BC). The imperial power base of this Syracusan tyrant stemmed from a huge naval fleet of 300 tetreras and penteras. After he ended Carthaginian authority in Sicily, he turned against the Etruscans. He made use of the Celtic invasion of Italy, and the Celts became his allies in the Italian peninsula (386 - 385 BC). This alliance was crucial for his politics, then focusing on the Adriatic Sea, where the Liburnians still dominated. In light of this strategy, he established a few Syracusan colonies on the coasts of the Adriatic Sea: Adria at the mouth of Po river and Ancona at the western Adriatic coast, Issa on the outermost island of the central Adriatic archipelago (island of Vis) and others. Meanwhile, in 385-384 BC he helped colonists from the Greek island of Paros to establish Pharos (Starigrad) colony on the Liburnian island of Hvar, thus taking control of the important points and navigable routes in the southern, central and northern Adriatic.
This caused a simultaneous Liburnian resistance on both coasts, whether in their ethnic domain or on the western coast, where their possessions or interests were in danger. A great naval battle was recorded a year after the establishment of Pharos colony, by a Greek inscription in Pharos (384 – 383 BC) and by the Greek historian Diodorus Siculus (80 – 29 BC), initiated by conflicts between the Greek colonists and the indigenous Hvar islanders, who asked their compatriots for support. 10,000 Liburnians sailed out from their capital Idassa (Zadar), led by the Iadasinoi (people of Zadar), and laid siege to Pharos. The Syracusan fleet positioned in Issa was informed in time, and Greek triremes attacked the siege fleet, taking victory in the end. According to Diodorus, the Greeks killed more than 5,000 and captured 2,000 prisoners, ran down or captured their ships, and burned their weapons in dedication to their god.