The island was first mentioned in written documents by a 6th century lexicographer Stephen from Byzantium, who referred to it as Ladesta and Ladeston. His source was Theopompus, a 4th century BC Greek historian and orator.
Although the oldes written document on Lastovo dates back to the 6th century, traces of human presence on the island, found in a cave called Račja spilja, prove a constant presence of man since stone age (8500 BC).
The names of numerous other Illyric settlements along the coast had the same suffix -est which indicates their Illyric origins. When the Romans conquered Dalmatia, they gave the island the Latin name Augusta Insula, meaning "emperor's island".