According to the Gesta Hungarorum by Bele Regis Notarius, Laborec was a Slavic ruler in the 9th century who was a vassal of Great Moravia.
His existence is controversial as the only source that mentions him, Gesta Hungarorum, was written in the 13th century, more than 300 years after his presumed rule.
When Tsar Simeon the Great began expanding his Bulgarian Empire, he gained control of a segment of territory, forcing Laborec to recognize his authority at the end of the 9th century.
In 896 the Hungarian tribes crossed the Carpathian Range and migrated into Pannonian Basin.
According to a number of modern historians Laborec was not a real person,[4][5][6] and some consider him a ruler of White Croats.