Carnac stones, Prehistoric stone alignment in Carnac, France.

The Carnac stones (Breton: Steudadoù Karnag) are a group of megalithic sites near the south coast of Brittany, made of weathered granite from local outcrops. They comprise four main alignment sites — Ménec, Kermario, Kerlescan and Petit-Ménec — plus dolmens, tumuli and single menhirs, with more than 3,000 standing stones in all. The rows run in long, roughly parallel lines across open grass, and the largest blocks, about 4 metres high, stand at the wider western ends.

The site was created between 4500 and 3300 BC by prehistoric communities during the Neolithic period in Europe. Later inhabitants sometimes used the stones as building material, and over the centuries some rows disappeared or were disrupted by farming and settlement.

Local stories describe these formations as Roman soldiers turned to stone by the wizard Merlin during his journey through Brittany. The oral tradition connects the site to medieval legend and remains part of how people in the region share the place with visitors today.

The rows are fenced off for most of the year; outside the summer season visitors may walk among the stones, while in July and August access is limited to guided tours and marked paths. The Maison des Mégalithes at the Ménec site provides orientation, and the Ménec rows are the easiest to reach on foot from the village of Carnac.

The height of the stones gradually decreases from west to east, ranging from about 4 meters (13 feet) at the western end to less than one meter (3 feet) at the eastern finish. This gradation follows a clear pattern whose purpose has never been definitively explained.