Transilien is the brand name given to the commuter rail network serving Île-de-France, the region surrounding and including the city of Paris. The network consists of nine lines: H, J, K, L, N, P, R, U, and V each operated by SNCF, the state-owned French railway company. The lines begin and end in major Parisian stations, except for lines U and V which connect major stations outside the Paris city borders. Unlike the RER network, the Transilien trains do not cross through the Paris city centre.

Commuter rail, or suburban rail, is a passenger rail transport service that primarily operates within a metropolitan area, connecting commuters to a central city from adjacent suburbs or commuter towns. Commuter rail systems are considered heavy rail, using electric or diesel trains. Distance charges or zone pricing may be used.