Sydney Metro (known during early planning and construction as Sydney Rapid Transit) is an automated rapid transit system under construction in Sydney, New South Wales, Australia. The first dedicated rapid transit line to be constructed is a link from Rouse Hill to Epping. The new line will connect to the existing Epping to Chatswood railway line, which will be converted to rapid transit standards; the project is called Sydney Metro Northwest and is expected to open in 2019.

Construction has commenced for Sydney Metro City & Southwest, an extension across Sydney Harbour and through the Central Business District (CBD), which will then take the trains to Bankstown. The line is expected to open in 2024.Sydney Metro West, a separate line between the Sydney CBD and Parramatta, is expected to open in the second half of the 2020s.

Sydney will be the first Australian city to build a full-fledged high-capacity rapid transit system. Plans and projects involving a high speed, rapid transit underground railway in Sydney date at least back to 2008, although an initial proposal was raised as early as 2001. Despite extensive plans for an underground network in the past, disputes over privatisation and funding had hampered government approval, delaying its inception. In spite of difficulties getting the project off the ground, government approval for what was initially known as the North West Rail Link, Sydney's first underground metro, was given in 2013. Route extensions and a name change to the Sydney Metro soon followed.

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