Unionville is a suburban district and former village in Markham, Ontario, Canada, 2 km (2.5 mi) northeast of Downtown Markham, 2 km (2.5 mi) west of Markham Village, and 33 km (20.5 mi) northeast of Downtown Toronto. The boundaries of Unionville are not well-defined. Several nearby neighbourhoods are claimed to be part of it however, this has been disputed between the various wards.

Markham is a city in York Region, Ontario, Canada. It is approximately 30 km (19 mi) northeast of Downtown Toronto. In the 2021 Census, Markham had a population of 338,503, which ranked it the largest in York Region, fourth largest in the Greater Toronto Area (GTA), and 16th largest in Canada.