Metro Trains Melbourne, often known simply as Metro, is the operator and brand name of train services on the electrified metropolitan rail network serving the city of Melbourne, Victoria, Australia. It is the largest urban rail network in Australia, with 17 lines and 222 stations across 405 km (252 mi) of railways, and the second busiest network in Australia, with a patronage of 182.5 million as of 2023–2024.

The network is owned by Public Transport Victoria who sublet the infrastructure and rolling stock to Metro Trains Melbourne, a joint venture between Hong Kong–based MTR Corporation (60%), John Holland Group (20%) and UGL Rail (20%). The three constituent companies are also partners in the Metro Trains Sydney joint venture, which has operated the Sydney Metro network since 2019. Metro Trains Melbourne took over as operator from Connex in 2009.

Metro Trains Melbourne operates a fleet of 269 six-car train sets on 998 kilometres (620 mi) of track. There are sixteen regular service rail lines and one special events railway line. Metro Trains Melbourne is also responsible for 222 railway stations and employs a workforce of 7,000 including train drivers, mechanical and electrical engineers, network operations specialists and station officers.

The railway track, infrastructure and rolling stock is owned by VicTrack on behalf of the State Government, and is leased to Public Transport Victoria which then sub-leases them to Metro Trains Melbourne. The State Government now also owns the name 'Metro,' and it will likely stay even if there is a change of operators. Metro Trains has faced criticism in the past and was voted the worst rail system in Australia in 2011. However, the operation, punctuality and consistency of the network has greatly improved since 2014 with level crossing removals, target benchmarks for trains and more frequent trains.

Metro Trains Melbourne was selected as the new operator by the Government of Victoria through its relevant agency, the Director of Public Transport, in June 2009 and replaced the previous operator, Connex Melbourne, on 30 November 2009. It was awarded an eight-year contract with the option of being extended for a further seven years. On 2 April 2012, the newly created Public Transport Victoria took over the management of the contract from the Director of Public Transport.

In May 2012, Australian Rail Tram and Bus Industry Union accused Metro Trains of taking shortcuts in safety procedures, including not checking on-board CCTV and intercoms, and allowing trains with cracked inner glass to take passengers. Metro Trains claim safety equipment is regularly checked during routine maintenance. It was reported in 2013 that tens of thousands of passengers were missing out on compensation when Metro failed to meet monthly performance targets, either because they were not aware of their entitlements or didn't want the hassle of going through a complicated claims system.

On 13 July 2017, Metro experienced a computer outage which resulted in 224 services being cancelled, and 378 services running late. Metro was fined a total of $1.2 million and was forced to reimburse $620,000 to the customers affected. Metro Trains chief Mike Haughton said: "A failure in the core train control system had meant operators could not see the trains, so it was shut down for safety reasons."

In September 2017 the state government extended the contract with Metro Trains until November 2024. It was later extended to May 2026, then until November 2027.