The Toronto subway and RT is the main rapid transit (RT) railway system in Toronto, Ontario, Canada. It is run by the Toronto Transit Commission (TTC). Since the first part under Yonge Street opened in 1954 with 12 stations, the system has grown to be Canada's biggest rapid transit rail system. It has four lines and 69 stations on 68.3 km of track. The subway system is used very often and has the most number of passengers of any system in Canada. It has an average of 948,100 passenger trips each weekday (as of 2010).

The system is was made bigger on the western part of the Yonge–University Line with new tracks and stations being made north to York University, Steeles Avenue, and Vaughan Corporate Centre in York Region. The Government of Ontario said on March 23, 2006 that it will give $670 million for this new work, which is less than one-third of the total money needed. The new track is about 8.6 km long and was built with six new stations: Downsview Park, Finch West, York University, Pioneer Village, Highway 407, and the Vaughan Metropolitan Centre. It was expected to cost about $2 billion.