The Metro-Cammell EMU (also known as M-Train or Modernisation Train, Chinese: 港鐵現代化列車) is the oldest type of electric multiple unit that operates on the MTR rapid transit railway system in Hong Kong.

A total of 768 cars were built by Metro-Cammell in England (and its successor GEC-Alsthom, later known as Alstom) between 1977 and 1994, and refurbished from 1998 to 2001 by United Goninan.

At the time of its introduction in 1979, the MTR M-Train EMU was believed to have the highest capacity of any metro car in the world.

[3] Although another set of EMU trains from the same manufacturer operated on the East Rail line, there were some significant differences between the two models.

The Metro Cammell EMUs of the East Rail line, which are also known as the Mid-Life Refurbishment Train, were formerly operated by the Kowloon-Canton Railway until being taken over by the MTR in 2007.

Statues of well-known Disney characters are included inside of the trains, such as Mickey Mouse and Donald Duck.

The refurbished front has a silver and black coating with new electronic destination and train running number displays.

The interior changes include the replacement of lighting and seats, along with installation of new dot-matrix display showing news and weather information, and flashing system maps indicating the station and line that the train is running on.

Some other changes included altering the fibreglass facade on the exterior ends to modernise their appearance, as well as the installation of the advanced digital voice announcement (DVA) and passenger information systems.

In August 2024, the MTR decorated one of the M-trains in a retro livery similar to its pre-refurbishment appearance as part of its 45th anniversary events.

[6] The traction system of M-Stock and T-Stock trains were changed to Chopper from Camshaft in 1992–1995, which gives them the present name CM-Stock and CT-Stock.

All I-Stock trains belong to Island line, excluding A126/A255, which transferred to the Tsuen Wan Line as an I-Stock (of which 3 cars were scrapped as they were damaged beyond repair in 2019, while the other 5 carriages were transferred to Siu Ho Wan Depot and some were subsequently scrapped in 2022).

When the construction of the Modified Initial System came underway in 1975, bidders for the rolling stock included Australia's Comeng (Commonwealth Engineering), Belgium's BN (La Brugeoise et Nivelles) and ACEC (Ateliers de Constructions Electriques de Charleroi), Canada's Hawker Siddeley Canada and Bombardier Transportation, Germany's MAN SE, and Britain's Metro-Cammell.

The MTRC signed a contract in March 1992 for 64 new rail cars (48 motorcars, 16 trailers) with an option for an additional 24 carriages.

Full withdrawal began the night of 10 September 2022, and retired trains were brought to Siu Ho Wan Depot for cutting and transporting away to scrapyards in River Trade Terminal near Tuen Mun.

In the early-1980s, Metro Cammell and GEC Traction proposed a version of the MTR M-Train EMU for Singapore's Mass Rapid Transit (MRT) metro system (which eventually opened in 1987), alongside several other bidders from France, Canada, West Germany, Sweden and Japan.

[17][18] Although Metro Cammell was shortlisted along with the Swedish ASEA and the Japanese Kawasaki Heavy Industries-led consortium, its eventual loss to the aforementioned Kawasaki consortium in winning what later became Contract 151 for Singapore's first metro rolling stock type was reported to be the relative energy inefficiency of the GEC Traction camshaft traction system then used by all MTR M-trains.

Another factor was a measuring error involving the London Underground 1983 Stock during the evaluation phase for Contract 151.

[19][20] The loss of said contract was a massive financial blow to Metro Cammell, who was forced to reduce their workforce by half in August 1984,[21] and was eventually acquired by GEC-Alsthom (now Alstom) in 1989.