Ontario Highway 80

King's Highway 80
Route information
Maintained by the Ministry of Transportation
Length	69.6 km[1] (43.2 mi)
Existed	August 11, 1937[2]–April 1, 1997[3]
Major junctions
West end	St. Clair Parkway (old Highway 40) in Courtright
Major intersections	Highway 40 – Sarnia  Highway 21 – Petrolia, Oil Springs  Highway 79 – Alvinston
East end	Highway 2 in Strathburn
Location
Country	Canada
Province	Ontario
Towns	Courtright, Brigden, Glencoe, Strathburn
Highway system
Ontario provincial highways Current Former 400-series
← Highway 77 → Highway 85
Former provincial highways ←  Highway 79 Highway 81  →

King's Highway 80, commonly referred to as Highway 80, was a provincially maintained highway in the Canadian province of Ontario. It travelled in an east–west direction south of Sarnia from Courtright to Strathburn. Beginning at the St. Clair Parkway near the shores of the St. Clair River, the route travelled 69.6 kilometres (43.2 mi), intersecting Highway 40, Highway 21 and Highway 79 before ending at Highway 2. In addition to the towns at either terminus, Highway 80 serviced the communities of Brigden, Glencoe and Alvinston. The entire route was and remains two lanes wide.

Highway 80 was first designated in 1937, travelling east from Highway 79 in Alvinston to Highway 2 in Strathburn. Most of the original winding highway was bypassed in 1962, and the route was extended west in 1963 to what was then Highway 40, now the St. Clair Parkway. It remained this way for over 30 years before being decommissioned as a provincial highway entirely in the mass downloading of highways in 1997. Today the route is known as County Road 80.