The MI 09 (French: Matériel d'Interconnexion de 2009, English: interconnection rolling stock of 2009) is a double-deck, dual-voltage electric multiple unit trainset that is operated on line A of the Réseau Express Régional (RER), a hybrid suburban commuter and rapid transit system serving Paris and its Île-de-France suburbs.

The Réseau Express Régional (RER) a hybrid suburban commuter and rapid transit system serving Paris and its suburbs.

[3] Barat Group performed various elements of the MI 09's assembly, such as the installation of secondary doors, lightings and miscellaneous electronics, a fireproof and soundproof cabin partitions, and other interior fittings.

[3] To facilitate speedy boarding times, each carriage features three wide doors on each side of the vehicle and floors that are level to the platforms.

High particle pollution in the underground RER stations in Paris have been a source of criticism in the past.

[3] Some of the style choices include boarding areas that provide a full view of both the upper and lower decks, an internal lighting system that uses porthole-shaped fixtures which designers say provide a more pleasant light, and seat fabric with a floral and plant theme.

As of 1 March 2022, 140 MI 09 trainsets were based at the Achères, Rueil-Malmaison, Sucy-en-Brie and Torcy RATP depots.