Helvetians, the ancient Celtic inhabitants of what is now western Switzerland. In 102 B.C. they invaded Italy, but were defeated by Marius. Julius Caesar routed them in 58 B.C., when they tried to cross into Gaul (France). The land of the Helvetians became part of the Roman Empire, and the inhabitants accepted Latin civilization. In the fourth century A. D. the region was overrun by Germanic tribes, and the Helvetians lost their identity among the invaders. Helvetia is the classical name for Switzerland.