The RER C is one of the five lines in the RER rapid transit system serving Paris, France. It is operated by SNCF.
The line runs from the northwestern terminuses Pontoise (C1), Versailles-Château (C5) and Saint-Quentin-en-Yvelines (C7) to the southeastern terminuses Massy-Palaiseau (C2), Dourdan-la-Forêt (C4), Saint-Martin d'Étampes (C6) and Versailles – Chantiers (C8).