Illyria (Ancient Greek Ἰλλυρία; Latin Illyria ; see also Illyricum) was in Classical antiquity a region in the western part of toay's Balkan Peninsula, founded by the tribes and clans of Illyrians, an ancient people who spoke the Illyrian languages. In Greek mythology, Illyrius was the son of Cadmus and Harmonia who eventually ruled Illyria and become the eponymous ancestor of the whole Illyrian people. The delineation of ancient Illyria can pose a problem to historians, since before the Roman conquest the Illyrians were not unified into an Illyrian kingdom, and Illyria's borders before Rome are not always clear. For example, the Dalmatae, though classed as an Illyrian tribe by language, were only subject to the kingdom of Illyria for a short time and soon defected during the reign of King Gentius.