The best known Celtic site in Switzerland is at La Tène on Lake Neuchâtel, which has given its name to the culture of the later Iron Age, beginning around 450 BC. The remains of two bridges along with thousands of iron weapons plus human and animal bones have been found there.

The Helvetians, who are remembered in the Latin name for Switzerland, Helvetia, were a Celtic tribe first mentioned at the end of the 2nd century BC. It is not known if they already lived in the the Swiss plateau area at that time, or if they moved there later. In 58 BC they attempted to migrate westwards, and burnt their towns to prevent a return. However, Julius Caesar defeated them at the battle of Bibracte and forced them back, in order to prevent Germanic tribes from moving southwards and taking their place on the Plateau.

The Lepontians settled in what is now Canton Ticino and the eastern parts of Canton Wallis, as well as in northern Italy. Inscriptions on some of their artefacts are written in characters of Etruscan origin.

The eastern part of modern-day Switzerland was inhabited by the Raetians (also spelt Rhetians or Rhaetians), who may have been related to the Etruscans. They gave their name to the Roman province of Raetia, which is why the Rumantsch language spoken in that area today is sometimes referred to as Raeto-Rumantsch.