The Doncaster railway line was a long-proposed suburban railway in the eastern suburbs of Melbourne, Victoria, Australia, that was anticipated to be built before December 2027, as a branch, along with the Hurstbridge line, of the planned future Clifton Hill Loop Line, as part of the 2013 PTV Network Development Plan.The Doncaster line would have primarily served the suburbs of Bulleen, Balwyn North, Kew, Templestowe and Doncaster, running along the median strip of the Eastern Freeway for most of its length.
First proposed in 1890, detailed planning commenced in 1969, and by 1972 the route was decided upon. Despite rising costs, the state governments of the period continued to make assurances that the line would be built. Property acquisition for part of the route was completed in 1975, and construction of a cutting at the city end commenced in 1974, only to be filled in two years later. By 1982 plans to build the line were shelved by the state government, and by 1984 land for the line once it left the freeway was sold by the Cain Labor government. In 1991 an independent report investigated constructing the line, recommending against it due to the high cost. However several other reports released since the 1970s detail the essential requirement for heavy rail mass transit in the Doncaster corridor.
The Doncaster rail line plan is almost identical to the Joondalup line, completed in 1992, and the Mandurah line, completed in 2007, both in Perth, a city with less than half the population of Melbourne. The Mandurah line runs along the centre median of the Kwinana Freeway and through various tunnels. It is almost double the length of the proposed Doncaster line and cost 1.6 billion; trains are able to travel at up to 130 km/h.
In 2017-18, as part of the proposed North East Link road project, the median of the Eastern Freeway is set to be removed as part of an upgrade with the addition of a new busway alongside the freeway. This means a rail line to Doncaster along the Eastern Freeway is unlikely to go ahead in the future. However a train service through Doncaster has continued to be proposed as part of the northern section of the Suburban Rail Loop.