The Rouge River is a river in Markham, Pickering, Richmond Hill and Toronto in the Greater Toronto Area of Ontario, Canada. The river flows from the Oak Ridges Moraine to Lake Ontario at the eastern border of Toronto, and is the location of Rouge Park, the only national park in Canada within a municipality. At its southern end, the Rouge River is the boundary between Toronto and southwestern Pickering in the Regional Municipality of Durham.

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.