Ontario Highway 18

King's Highway 18
Highway 18      Limited-access      King's Highway      Former highways
Route information
Maintained by Ministry of Transportation of Ontario
Length	76.0 km[1] (47.2 mi) (1997)
Existed	June 11, 1930[2]–January 1, 1998[3]
Major junctions
North end	Highway 3 in Windsor
East end	Highway 3 / Highway 77 (Talbot Street / Erie Street) in Leamington
Location
Country	Canada
Province	Ontario
Counties	Essex
Major cities	Windsor, LaSalle, Amherstburg, Malden Center, Harrow, Kingsville, Ruthven, Leamington
Highway system
Ontario provincial highways Current Former 400-series
← Highway 17B → Highway 19
Former provincial highways Highway 18A  →

King's Highway 18, commonly referred to as Highway 18, was a provincially maintained highway in the Canadian province of Ontario, located entirely within Essex County. Since 1998, the majority of the former route has been known as Essex County Road 20. The route travelled at the southernmost point in Canada, along or near the shoreline of the Detroit River and Lake Erie between Windsor and Leamington, with Highway 3 as the terminus at both ends. The former route provides access to the communities of LaSalle, Amherstburg, Malden Centre, Harrow, Kingsville and Union.

The original alignment of Highway 18 followed a completely different routing for the first 18 months of its existence than it would for the following 50 years. As it was first designated in 1930, Highway 18 provided a shortcut between Windsor and Tilbury. By early 1932, this route was renumbered as Highway 2, and a new highway between Windsor and Leamington via Amherstburg designated as Highway 18. Expansion of the highway to four lanes between Windsor and Amherstburg was first proposed in the mid-1960s, but not undertaken until the mid-1980s. In the mid-1990s, the route was determined to no longer be of provincial significance and was transferred—or downloaded—to the municipalities and township that it lay within. On April 1, 1997, Highway 18 was downloaded through LaSalle, as well between Union and Leamington; it was temporarily rerouted to end at Highway 3 in Ruthven. On January 1, 1998, the entire route was transferred to Essex County.