King's Highway 3, commonly referred to as Highway 3, is a provincially maintained highway in the Canadian province of Ontario which travels parallel to the northern shoreline of Lake Erie. It has three segments, the first of which travels from the Ambassador Bridge in Windsor to Highway 77 in Leamington. The second portion begins at Talbotville Royal outside of St. Thomas at Highway 4, and travels to the western city limits of Port Colborne. The road is regionally maintained within Port Colborne as Niagara Regional Road 3, but regains its provincial designation at Highway 140. Its third and final terminus is at Edgewood Park, within the Fort Erie town limits. From there, the road continues as Niagara Regional Road 3 to the Peace Bridge, where drivers can cross to the United States. The total length of Highway 3 is 258.2 km (160.4 mi), consisting of 49.2 km (30.6 mi) from Windsor to Leamington, 187.9 km (116.8 mi) from Talbotville Royal to Port Colborne and 21.1 km (13.1 mi) from Port Colborne to Edgewood Park.

Southwold is a township in Elgin County, in Ontario, Canada, located on the north shore of Lake Erie. It is a rich agricultural zone producing predominantly corn and soybeans. It is part of the London census metropolitan area.