Highway 66 is a provincial highway in the Canadian province of Ontario.

Located in the Timiskaming District, the highway begins at Matachewan at the junction of Highway 65, and extending eastward for 106 kilometres to the Quebec boundary just east of Kearns. At the provincial border, the highway continues eastward as Quebec route 117.

From Highway 11 (41 km east of Matachewan) at Kenogami Lake, Ontario eastwards to the Quebec border, Highway 66 is designated as part of the Trans-Canada Highway.

The main community on the highway is Kirkland Lake, Other Communities include:

• Matachewan
• Kenogami Lake, Ontario
• Swastika
• Chaput Hughes
• King Kirkland
• Larder Lake
• Virginiatown
• McGarry Township
• Kearns

Ontario provincial highways | Trans-Canada Highway