Central Ontario is a subregion of Southern Ontario in the Canadian province of Ontario which lies between Georgian Bay and the eastern end of Lake Ontario.

The population of the region was 1,035,792 in 2006; however, this number does not include large numbers of seasonal cottage country residents, which at peak times of the year swell its population to well in excess of 1.5 million. Although it contains many small and medium sized urban centres, much of Central Ontario is covered by farms, lakes (with freshwater beaches), rivers or sparsely populated forested land on the southern edge of the Canadian Shield.

Central Ontario is located within Southern Ontario. It is not geographically close to the actual "centre" of Ontario as its name would suggest, but in the central third of Southern Ontario on a horizontal west to east axis.

Parry Sound District and Muskoka District are within Central Ontario, but are treated as part of Northern Ontario by federal economic development programs because of these districts' special economic circumstances; Parry Sound, but not Muskoka, is now classed with Northern Ontario by the provincial government.

Ontario /ɒnˈtɛərioʊ/ is one of the provinces of Canada, located in east-central Canada. It is Canada's most populous province or territory and fourth largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa.

Ontario is bordered by the province of Manitoba to the west, Hudson Bay to the north, Quebec to the east, and to the south by the U.S. states of Minnesota, Michigan (portions to the west), New York (portions to the east), Ohio and Pennsylvania. All but a small part of Ontario's 2,700 km (1,677 mi) border with the United States follow inland waterways: from the west at Lake of the Woods, eastward along the major rivers and lakes of the Great Lakes/St. Lawrence River drainage system. These are the Rainy River, the Pigeon River, Lake Superior, the St. Mary's River, Lake Huron, the St. Clair River, Lake St. Clair, the Detroit River, Lake Erie, the Niagara River, Lake Ontario, and along the St. Lawrence River from Kingston, Ontario to the Quebec boundary just east of Cornwall, Ontario.