The SNCF Class Z 20900 is a double-deck, dual-voltage electric multiple unit trainset that is operated on line C of the Réseau Express Régional (RER), a hybrid suburban commuter and rapid transit system serving Paris and its Île-de-France suburbs. The 54 four-car trains were built by a consortium of French manufacturer Alstom and Canadian conglomerate Bombardier between 1998 and 2004. The first set was placed into regular passenger service in July 2001. They are the final equipment produced as part of the Z 2N series of trainsets, which were continuously improved over several generations.