Ermont Eaubonne to Champ-de-Mars line, also known as the Vallée de Montmorency - Invalides (VMI) line, is a French railway line in the Île-de-France region, part of the RER C line. It connects the Champ de Mars - Tour Eiffel station in Paris with the Ermont - Eaubonne station in the Val-d'Oise department, fifteen kilometers north of the capital. It forms line n° 962 000 of the national rail network.
The VMI brings together two old lines with specific histories: the Auteuil line, which became part of the Petite Ceinture line within Paris, and the line from La Plaine to Ermont-Eaubonne, the Grésillons line. The VMI project, developed in 1977, was designed to replace the significant north-south RER transversal planned in the 1965 SDAU. The line was inaugurated on September 25, 1988, after three years of construction and a complicated gestation period marked by technical difficulties and strong opposition from residents. It is served by Z 2N railcars, with a service frequency of four trains per hour in each direction during off-peak hours and eight trains per hour during rush hours, with freight traffic mainly serving the port of Gennevilliers.