York County, Ontario

York County
Dissolved county (Restructured as regional municipality)
York County c. 1880s
Colony/Province	Upper Canada (1792–1841) Province of Canada (1841–1867) Ontario (1867–1971)
Incorporated	1792 (created from Home District)
Dissolved	1971 (reorganized into the Regional Municipality of York)
County seat Administrative seat	York (1792–1834) Toronto (1834–1953) Newmarket (1953–1971)
Area
• Total	2,392.17 km2 (923.62 sq mi)
	The following figure was the size of the county from 1851 to 1953
Time zone	UTC−05:00 (Eastern)

York County is a historic county in Upper Canada, Canada West, and the Canadian province of Ontario. It was organized by the Upper Canada administration from the lands of the Toronto Purchase and others.

Created in 1792, at its largest size, it encompassed the area that presently comprises the City of Toronto, the regional municipalities of Halton, Peel, and York as well as portions of Regional Municipality of Durham and the City of Hamilton. However by 1851, York County only consisted of the areas presently comprising Toronto and Regional Municipality of York. In 1953, York County was split again, with the area south of Steeles Avenue forming the Municipality of Metropolitan Toronto.

York County was formally dissolved in 1971, with its remaining municipalities reorganized as the Regional Municipality of York.