The R21 is a major north–south provincial route (with a freeway portion designated as a National Road) in eastern Gauteng Province, South Africa.

As the eastern of the two freeways, it links the Pretoria city centre with OR Tambo International Airport and Boksburg.

The route intersects the N1 highway (Eastern Pretoria Bypass; Danie Joubert Freeway) near Centurion, the R24 near the airport, the N12 and N17 in Boksburg, and the N3 near Vosloorus on the East Rand, where it ends.

[5] The South African government announced on 28 March 2024[6] that e-tolls in Gauteng would officially be shut down on 11 April 2024 at midnight,[7][8] therefore returning the R21 to being a toll-free route.

Further south, at the suburb of Boksburg North, the R21 meets the M41 again and continues by way of a right turn to become Rondebult Road.

The R21 then meets the R29 (Cason Road) and continues south, passing to the west of Boksburg Central.

[2] After Boksburg Central, the R21 crosses the N17 highway at Elspark and continues south through Sunward Park.