The Black River is a river in the Regional Municipality of York and the Regional Municipality of Durham in Central Ontario, Canada.

[4] The river begins at an unnamed lake on the Oak Ridges Moraine in Whitchurch–Stouffville, York Region, near the community of Cedar Valley.

It heads northwest, under the Canadian National Railway main line, and then north into East Gwillimbury, then flows northeast under Ontario Highway 48 to cross the northwestern corner of Uxbridge, Durham Region.

It heads north, passes over the Baldwin Dam at the community of Baldwin, flows through the community of Sutton, and reaches its mouth at Lake Simcoe between the communities of Briars Park to the west and Mossington Park to the east.

[5] The Sutton-Zephyr rail trail occupies a portion of the abandoned Lake Simcoe Railway branch of the Toronto and Nipissing Railway that crosses the Black River.