The province of Ontario does not have a single unified network of controlled-access highways or freeways. Although most freeways are part of the 400-series highways, which can be characterized by their high design standard, several other sections of provincial highways are also classified as freeways. Additionally, several controlled-access highways, called municipal expressways, are maintained by municipalities rather than the provincial government like provincial highways are.
The following is a list of freeways in Ontario as defined by the Official Road Map of Ontario published by the Ministry of Transportation of Ontario (MTO). The MTO defines a freeway as a divided highway with at least two lanes in each direction.
All 400-series highways are freeways for their entire length.
Some non 400-series highways are also freeways for some of all of their length.
Municipal expressways are expressways not under the jurisdiction of the provincial government. Instead, they are maintained by the municipal governments of the municipalities they are located in. They can vary in size and infrastructure, ranging from major arterial roads (e.g. Cootes Drive, Hamilton) to control access freeways (e.g. Gardiner Expressway, Toronto).