King's Highway 407, commonly referred to as Highway 407 and colloquially as the "four-oh-seven", is a tolled 400-series highway in the Canadian province of Ontario. Comprising a privately leased segment as well as a publicly owned segment, the route spans the entire Greater Toronto Area (GTA) around the city of Toronto, travelling through the suburbs of Burlington, Oakville, Mississauga, Brampton, Vaughan, Markham, Pickering, Whitby, and Oshawa before ending in Clarington, north of Orono. At 151.4 km long, this is the fourth-longest freeway in Ontario's 400 series network, after Highways 417, 400, and 401. The segment between Burlington and Brougham in Pickering is leased to and operated by the 407 ETR Concession Company Limited and is officially known as the 407 Express Toll Route (407 ETR). It begins at the junction of the Queen Elizabeth Way (QEW) and Highway 403 in Burlington, and travels 108.0 km (67.1 mi) across the GTA to Brock Road in Pickering. East of Brock Road, the tollway continues east as Highway 407, a toll route operated by the provincial government, for 43.4 km (27.0 mi) to Highway 35/115 in Clarington. The route interchanges with nine freeways: the QEW, Highway 403, Highway 401, Highway 410, Highway 427, Highway 400, Highway 404, Highway 412, and Highway 418. Highway 407 is an electronically operated toll highway; there are no toll booths along the length of the route. Distances are calculated automatically using transponders or automatic number-plate recognition, which are scanned at entrance and exit portals.

The 400-series highways are a network of controlled-access highways in the Canadian province of Ontario, forming a special subset of the provincial highway system. They are analogous to the Interstate Highway System in the United States or the Autoroute system of neighbouring Quebec, and are regulated by the Ministry of Transportation of Ontario (MTO). The 400-series designations were introduced in 1952, although Ontario had been constructing divided highways for two decades prior. Initially, only Highways 400, 401 and 402 were numbered; other designations followed in the subsequent decades. The network is situated almost entirely in Southern Ontario, although Highway 400 extends into the more remote northern portion of the province.