Montesson (French pronunciation: [mɔ̃tesɔ̃]) is a commune in the Yvelines department in the Île-de-France region in north-central France.

It is located in the western suburbs of Paris.

The T ticket is also valid on the entire metro (Paris and suburbs) on the RER lines of the RATP and the SNCF.

It is sold for a single price of 1.70 € for a journey or 12.50 € for a book of 10.

It can be purchased all around the Ile de France metro stations, RER stations, bus terminals, and RATP authorized dealers.