King's Highway 427, also known as Highway 427 and colloquially as the 427, is a 400-series highway in the Canadian province of Ontario that runs from the Queen Elizabeth Way (QEW) and Gardiner Expressway in Toronto to Major Mackenzie Drive in Vaughan. It is Ontario's second busiest freeway by volume and the third busiest in North America, behind Highway 401 and Interstate 405 in California. Like Highway 401, a portion of the route is divided into a collector-express system with twelve to fourteen continuous lanes. Notable about Highway 427 are its several multi-level interchanges; the junctions with the QEW/Gardiner Expressway and Highway 401 are two of the largest interchanges in Ontario and were constructed between 1967 and 1971, while the interchanges with Highway 409 and Highway 407 were completed in 1992 and 1995, respectively.

The local–express lane system is an arrangement of carriageways within a major highway where long distance traffic can use inner express lanes with fewer interchanges compared to local traffic which use outer local lanes that have access to all interchanges. This can also be called a collector/distributor lane system within a single interchange. One of the longest examples is Highway 401 in Toronto, where highway ramps between express and local lanes cross over one another; these are commonly known as braided ramps.