Highway 21 is a cross-border spur in the Regional District of Central Kootenay in British Columbia.

Approximately 4 km (2.49 mi) from its northbound terminus, Highway 21 comes to an intersection with Erickson Street as it enters Creston.

At this point, motorists intending to travel eastbound on the Crowsnest Highway toward Cranbrook and the Alberta border can bypass Creston's main business district and connect to the Crowsnest at Erickson.

Westbound motorists can continue on Highway 21 to its northern terminus.

[2] The entire route is in Central Kootenay Regional District.