Helvetia (hĕlvĕˈshə) [key], region of central Europe, occupying the plateau between the Alps and the Jura mts. The name is derived from the Roman term for its inhabitants, the predominantly Celtic Helvetii, who were defeated (58 B.C.) at Bibracte by Julius Caesar in the Gallic Wars. The Helvetii later prospered under Roman rule; their achievements are evidenced by the remains at Avenches. Helvetia corresponds roughly to the western part of modern Switzerland, and the name is still used in poetic reference to that country and on its postage stamps.