Unionville GO Station is a train and bus station in the GO Transit network located in Markham, Ontario, Canada. It is a stop on the Stouffville line. The station is also served by Highway 407 East Express buses, which run westbound to Highway 407 station, northbound to Mount Joy GO Station, and eastbound to the Oshawa GO station.

By late May 2022, the station had acquired a second track, a turnaround track and an island platform to support future all-day, two-way service on the Stouffville line. In the future, GO trains will run every 10 minutes to Unionville and every 30 minutes to Mount Joy GO Station.

The original Unionville station was opened in 1871 by the Toronto and Nipissing Railway. The railway line and station were acquired in succession by the Midland Railway of Canada in 1882, the Grand Trunk Railway in 1884 and Canadian National Railway in 1923. Canadian National served the station until 1978; GO Transit used the station from 1982 to 1991. GO train service ended at the station on Friday May 3, 1991, and service began at the current GO station the following Monday, May 6.

The old station building has been restored and is now used as a community centre. Like Markham GO Station, this station features classic Canadian Railway Style with elements of Vernacular Carpenter Gothic architecture of the 19th Century. It is located on Station Lane, near Main Street Unionville. While a platform exists it is fenced off from the rail line to indicate it is not an operational station.

The current station was built in 1991 to replace the old Unionville Station. The newer station was renovated and re-opened in April 2005 and accessed by a service road from Kennedy Road north of Highway 407.

By the end of May 2022, Metrolinx had completed a number of station improvements as part of GO Expansion to support future all-day, two-way service on the Stouffville line. The improvements include:

• A second track, new platform and a turnaround track.
• A new island platform and a relocated east platform, both with canopies, shelters and a snow-melting system.
• New pedestrian tunnels and elevators.
• 286 additional parking spots.
• Pedestrian walkways through the parking lot.
• New ramps from the parking lot to the platforms.
• More bicycle storage.

• 52 407 East (Oshawa–Highway 407 Bus Terminal) (weekend only)
• 54 407 East (Markham–Highway 407 Bus Terminal) (weekdays only)
• 56 407 East (Oakville GO Station–Oshawa GO Station) (weekdays only)
• 56A 407 Corridor (Square One - Oshawa GO Station) (weekday express)
• 71 Stouffville ("Train-bus" for Stouffville Line when trains do not operate)

• 8 Kennedy
• Viva Purple (at University Boulevard)

Viva service began on October 16, 2005, with buses stopping near Kennedy Road. Because the nearby Enterprise Drive was not finished when Viva services in the area began, this station served as a temporary station until November 19, 2005. During this time, both Viva Purple and Viva Green buses had to go on a detour on Highway 407 nearby. Viva Pink services were added on January 2, 2006.

Unionville was the eastern terminus of the now defunct Viva Pink service to Richmond Hill Centre and Finch station.

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• Media related to Unionville GO Station at Wikimedia Commons
• GO Transit station page for Unionville GO Station