The R42 is a provincial route in South Africa that connects Vanderbijlpark with Bronkhorstspruit via Vereeniging, Heidelberg, Nigel and Delmas.

It then intersects with the R23 road at an off-ramp junction just after the town centre and it continues west-south-west, becoming the southern border of the Suikerbosrand Nature Reserve.

At Peacehaven, the R42 turns southwards, following the Vereeniging Railway, to reach a junction with the R82 road, just west of the R82's Vaal River crossing.

Near the suburb of Powerville, the R42 meets the R59 Sybrand van Niekerk Freeway (west southbound and east northbound off-ramps only).

The R42 continues westwards as the main road through Vanderbijlpark, bypassing Sharpeville and passing the Vaal University of Technology.

As the road continuing westwards joins the N1 Kroonvaal Toll Route southbound, the R42 route makes a left turn to become Boundary Road southwards and continues for 15 kilometres, crossing the Vaal River adjacent to the Vaal Barrage into the Free State, crossing to the other side of the N1 toll highway, to end at another junction with the R59 road approximately 18 kilometres east of the city of Parys, just west of the R59's intersection with the N1 highway.