The A4042 is a trunk road that runs from Abergavenny to Newport in south Wales.

This section is a single carriageway and is winding and undulating.

From Little Mill onwards the road is dual carriageway, bypassing Pontypool and Cwmbran before crossing the city boundary into Newport.

The first section of which, Heidenheim Drive (named after one of Newport's twin towns), is an elevated roadway through the Crindau district.

The road then becomes the Kingsway that passes through Newport city centre, and continues on as Usk Way until its junction with the A48 Southern Distributor Road to the south of Newport.