Simcoe County is located in central portion of Southern Ontario, Canada. The County is situated just north of the Greater Toronto Area stretching from the shores of Lake Simcoe in the east to Georgian Bay in the west. Simcoe County forms part of the Greater Golden Horseshoe area, a densely populated and industrialized region centred around the Greater Toronto Area.

The land area of the county is 4,859.16 square kilometres (1,876.13 sq mi). The elevated Niagara Escarpment runs through sections of the western part of the county and the Minesing Wetlands, a Ramsar Convention Wetland Of International Importance, is located in the central area of the County.

The county administrative centre is located in Midhurst, outside of Barrie.

Although not politically recognized, Simcoe County is informally split into two subregions, “South Simcoe” and “North Simcoe”. The dividing line between these two areas is Simcoe County Road 90 (Mill St.).

South Simcoe municipalities are situated at the northern boundary of the Greater Toronto Area (GTA) and therefore generally have a closer socio-economic association with the GTA. South Simcoe is also within the Toronto commuter-belt as it is home to a relatively high proportion of people commuting to the GTA. South Simcoe is home to five municipalities, including: the Town of Innisfil, the Township of Adjala-Tosorontio, the Town of Bradford West Gwillimbury, the Township of Essa and the Town of New Tecumseth (which includes: Alliston, Beeton, & Tottenham).