Donald Cousens Parkway or York Regional Road 48, also referred to historically as the Markham Bypass or Markham Bypass Extension, is a regionally maintained arterial bypass of Markham in the Canadian province of Ontario. Named for former Markham mayor Don Cousens in April 2007, the route initially travelled northward from Copper Creek Drive in Box Grove, south of Highway 407, to Major Mackenzie Drive (York Regional Road 25). A southern extension to Steeles Avenue was later completed and the name Donald Cousens Parkway applied along the extension to Ninth Line. In addition to its role of funneling through-traffic around downtown Markham, the route serves as a boundary to residential development as land to the north and east are part of the protected Rouge Park and southwest limits of the planned Pickering Airport.