| Province: | AB |
| Type: | AB 1970s |
| Route: | 21A |
| Decommissioned: | 1990s |
| Section1: | Southern segment |
| Length Km1: | 33 |
| Direction A1: | South |
| Direction B1: | North |
| Terminus B1: | near Carbon |
| Terminus A1: | in Beiseker |
| Section2: | Northern segment |
| Length Km2: | 5 |
| Direction A2: | West |
| Direction B2: | East |
| Terminus A2: | near Nevis |
| Terminus B2: | near Nevis |
| Rural Municipalities: | Rocky View County, Kneehill County, County of Stettler No. 6 |
| Villages: | Beiseker, Acme |
| Previous Type: | Hwy |
| Previous Route: | 21 |
| Next Type: | Hwy |
| Next Route: | 22 |
Alberta Provincial Highway No. 21A, commonly referred to as Highway 21A, was the designation of two former spur routes of Highway 21 in Alberta, Canada.
The southern section of Highway 21A was a highway which started at Highway 9 in the Village of Beiseker and traveled north for to the Village of Acme and then turned east for to Highway 21, northeast of the Village of Carbon. It was established in 1958/59 when Highway 21 was realigned from Beiseker to Highway 1 (Trans-Canada Highway) east of Strathmore.[1] [2] Highway 21A was renumbered to Highway 26 in 1962/63,[3] [4] and in 1972/73 the north-south section became Highway 806 while the east-west section became Highway 575.[5] [6]
The northern section of Highway 21A was a highway that connected Highway 21 with Highway 12 near the Hamlet of Nevis. In the early-1990s, Highway 11 was extended east from Highway 815 near Joffre to Highway 21; when construction was completed, Highway 21A became part of Highway 11.[7] [8]