Sydney Trains is the suburban passenger rail network serving the city of Sydney, New South Wales, Australia. The network is a hybrid suburban-commuter railway with a central underground core that covers over 815 km (506 mi) of track and 178 stations over 7 lines. The network has 21 hours a day operation with train frequencies of every three minutes or better in the underground core, 5–10 minutes at most major stations all day, 15 minutes at most minor stations all day and four trains an hour on the Cumberland Line. During weekend services trains are less frequent with headways of upwards of a half-hour on outer stations with frequencies of less than 10 minutes in the underground core.

The network is controlled by the New South Wales Government's transport authority, Transport for NSW, and is part of the authority's Opal ticketing system. In 2015-16, 322 million passenger journeys were made on the network.

The Sydney Trains network is operated by a government owned organisation–also called Sydney Trains–that replaced the previous government operator, RailCorp. In May 2012 the Minister for Transport announced a restructure of RailCorp. This resulted in all suburban services in the Sydney Metropolitan area bounded by Berowra, Emu Plains, Macarthur and Waterfall transferring from RailCorp's CityRail division to Sydney Trains on 1 July 2013. Intercity and Hunter Line services previously operated by CityRail are now operated by NSW TrainLink which was also formed as part of the restructure. RailCorp was left as the owner of the network infrastructure.

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