The Regional Municipality of York, also called York Region, is a regional municipality in Southern Ontario, Canada, between Lake Simcoe and Toronto. It replaced the former York County in 1971, and is part of the Greater Toronto Area and the inner ring of the Golden Horseshoe. The regional government is headquartered in Newmarket.

The 2016 census population was 1,109,909, with a growth rate of 7.5% from 2011 to 2016. The Government of Ontario expects its population to surpass 1.5 million residents by 2031.