Alberta Provincial Highway No. 21, commonly referred to as Highway 21, is a north-south highway in Alberta, Canada that parallels Highway 2 between Calgary and Edmonton. It is approximately 328 kilometres (204 mi) in length. It begins at the Trans-Canada Highway (Highway 1) east of Strathmore, and ends at Fort Saskatchewan where it is succeeded by Highway 15. The northernmost 25 kilometres (16 mi) of the highway are twinned. Highway 21 runs roughly parallel to the main north-south CN rail line between Calgary and Edmonton between Three Hills and Looma.