Kitchener is one of the seven train lines of the GO Transit system in the Greater Toronto Area, Ontario, Canada.

It extends westward from Union Station in Toronto to Kitchener, though most trains originate and terminate in Brampton in off-peak hours.

[3] In September 2019, GO Transit introduced limited off-peak train service along the entire length of the line, with two new weekday round trips operating between Toronto and Kitchener outside of peak periods.

[9] On April 8, 2023, hourly weekend service was introduced between Mount Pleasant and Union, with Kitchener express bus connections at Bramalea.

[16] It drew criticism from Weston community groups, which opposed the increased use of diesel locomotives on the basis of air pollution.

Electrification plans reaffirmed overall Metrolinx goals of track bed and bridge improvements, quad-tracking sections of the line, and the addition of a station at Breslau.

Outside of peak periods, service operates hourly between Mount Pleasant and Union, of which two off-peak in each direction also cover the entire route from Kitchener to Toronto.

[25] The provincial initiative known as GO Regional Express Rail proposes a substantial increase in Kitchener line service over the next decade.

Electrification will be in place from Bramalea to Union Station, with trains running every 15 minutes along the electrified line throughout the day.

[22] As part of Toronto mayor John Tory's Smart Track initiative, new stations are planned where the line crosses St. Clair Avenue West and near Liberty Village.

[31] In February 2020, Metrolinx held a series of Public Information Centres detailing plans for expansion on the line.

[32] On April 30, 2021, the Ontario Ministry of Transportation and Metrolinx released a preliminary business case for mid-term infrastructure improvements which would permit more frequent Kitchener line service, as well as a Request for Qualifications for smaller, short-term infrastructure improvement projects on the line.

[33] The business case, dated to March 2021, estimated a reduction of GO train travel times from Kitchener to Toronto's Union Station from 111 minutes to 98 minutes with infrastructure improvements which would lift existing slow orders on the line due to poor infrastructure repair.