RER E

RER E is one of the five lines in the Réseau Express Régional (English: Regional Express Network), a hybrid commuter rail and rapid transit system serving Paris and its suburbs. The 60-kilometre (37 mi) line travels between western and eastern suburbs, with all trains serving the stations in central Paris, before branching out towards the ends of the line.

The line runs from the western terminus Nanterre–La Folie (E1) to the eastern termini Chelles–Gournay (E2) and Tournan (E4). It is operated by SNCF. It is the most interconnected line in the Île-de-France region, with connections to all 4 other RER lines, 10 out of the 14 Metro lines (as well as 3 of the future lines of the Grand Paris Express), 6 lines of the Transilien commuter rail service, 4 Tramway lines, and hundreds of bus routes. Six of the top ten busiest train stations in France are accessible via RER E, including three of Paris' mainline stations: Gare du Nord, Gare de l'Est and Gare Saint-Lazare.

Originally referred to as the Est Ouest Liaison Express or EOLE (English: East West Express Link), RER E is the newest RER line in the system, opening in 1999. An extension to Tournan opened in 2003. The first phase of a western extension opened on 6 May 2024, extending the line to Nanterre–La Folie, with a further extension to Mantes-la-Jolie under construction and planned to open in early 2027. It served over 400,000 passengers a day as of March 2025, with expectations of 600,000 daily passengers once the extension has been completed.