The Harris trains are the first steel-bodied electric multiple unit (EMU) trains to operate on the suburban railway network of Melbourne, Victoria, Australia. They were introduced in 1956, by the Victorian Railways, and last operated in 1988, although a number of the carriages were converted for other uses and are still operating. They were named after Norman Charles Harris, Chairman of Commissioners of the Victorian Railways, between 1940 and 1950.

The Harris trains were commonly referred to as "Blue Trains" due to their deep blue livery, complemented by a yellow band about halfway up the body. Royal blue and yellow were common colours for the Victorian Railways passenger rolling stock in the post-war era.

The trains had a saloon seating layout, divided into smaller sections by full-height partitions. They were provided with either two or three sets of hand-operated dual sliding doors on each side of the carriage. Later Harris sets were fitted with power doors. Carriages were designated as first or second class until 1958, when one-class suburban travel was introduced. Interiors were split into smoking and no-smoking compartments until late 1978, after which smoking on trains was prohibited. Most of the carriages were delivered without end gangways between carriages, but safety concerns led to them being added in the final five sets delivered from mid-1966. Those sets were also fitted with only two doors per carriage side rather than three, permitting additional seating and reflecting the increasing average travel distance.

The first thirty trains were fitted with automatic couplers at both ends of all carriages, and the second series with semi-permanent drawbars, except for the driving ends of motor carriages, and one end of BT ("backing trailer") carriages. Later, drawbars were fitted in the middle of first series blocks and units, although the final ten motor cars had automatic couplers at both ends.

First-series motor cars had 59 second-class seats and trailers 72 seats (first class in the T cars or second class in the BT cars), divided into smoking and non-smoking sections. For the second series the internal partitions were removed, and capacities increased to 65 and 80 passengers respectively for a total gain of 50 seats per seven-car train. Smoking was then only permitted in the middle third of each carriage. Later, a policy change saw smoking permitted in the whole of each Motor carriage, and not at all in trailers.

The first 30 7-carriage trains, known as the first series, were constructed in the United Kingdom by Gloucester Railway Carriage and Wagon Company, and delivered between 1956 and 1959. Another 30, the second series, were built by Martin & King in Melbourne, and delivered between 1961 and 1967. From 1966, these were delivered with end doors and gangways between carriages, allowing passengers to change carriages.

The first series of "T" and "BT" trailers were built by Comeng (the first 10 in Sydney, the rest in Melbourne), and finished by Martin & King, with the remainder built at the Newport Workshops. Between 1968 and 1970, ten additional motor carriages, built by the Victorian Railways' Newport Workshops, were delivered to provide for some Harris trains to be lengthened to eight carriages.

In 1970 and 1971, six new trailer carriages were built as prototypes for the next fleet (the Hitachi trains). These carriages were 75 feet (22.86 m) long, compared to 63 feet (19.20 m) of the earlier carriages, and were equipped with the mechanisms for power-closing doors, the first such use in Melbourne. However, it was not until the following year that a complete (4-carriage) train was used this way, after conversion of some motor carriages. These carriages were converted into H type carriages, for use in LH sets with V/Line, in the mid 1980s.