Celtic tribal confederation of the Swiss plateau, famous for their attempted mass migration to southwestern Gaul in 58 BCE that was stopped and reversed by Julius Caesar at the Battle of Bibracte, the opening campaign of the Gallic Wars.
Defeated by Caesar at Bibracte (58 BCE) and forced to resettle their original territory as a buffer/client state; gradually incorporated into the Roman province of Gallia Belgica/Germania Superior.
Caesar's own account opens with the Helvetii migration and their defeat at Bibracte, the primary ancient source for this polity.