Paris Métro Line 19

Paris Métro Line 19 is a new line of the Paris Métro that is planned as an expansion of Grand Paris Express. Officially announced on 22 November 2023, it is planned to connect Nanterre–La Folie at the west of La Défense business district to Charles de Gaulle Airport and the new area to be developed at Triangle de Gonesse. It will serve the residential areas of the department of Val-d'Oise, notably Argenteuil and Garges-lès-Gonesse, in order to make them more accessible and accelerate their urban renewal. According to the first studies, the line is expected to be opened by 2040.

Tracks and stations
During initial planning of Grand Paris Express, the authorities of the department of Val-d'Oise expressed criticism as it was poorly served by the new lines to be built. On 3 April 2023, while construction of the Grand Paris Express metro lines was already in progress, Valérie Pécresse announced that a new line 19 was planned to be added to the urban development plan of the Île-de-France region (SDRIF), as a request from the department of Val d'Oise. The initial routes to be considered were connections from Nanterre to Saint-Denis via Argenteuil and from Nanterre to Cergy also via Argenteuil.

On 22 November 2023, the Île-de-France region and the department of Val d'Oise announced jointly that the new line will eventually join Nanterre to Triangle de Gonesse, where it will connect to Line 17 heading to Charles de Gaulle Airport. The line would be from 25 to 30 km long, serving from 9 to 11 stations depending on the route chosen. It will be essentially underground and fully automated.

Funding
The Île-de-France region and the department of Val d'Oise will fund feasibility studies for an amount of 6 million euros. Total construction cost of the project is estimated at this stage from 5 to 6 billion euros. Financial support from the French government is being considered. According to the President of the Île-de-France region, Valérie Pécresse, the latter is not opposed to participating in the construction of this new line.