The A466 is about 30 miles (48 km) long and runs through the counties of Herefordshire and Gloucestershire in England, and Monmouthshire in Wales.

The road crosses the border between England and Wales at three places along its length: at Buckholt, Redbrook, and Bigsweir.

[4] Between Kingsthorne and Monmouth, the road passes through open countryside several miles to the west of the River Wye, and the villages of Wormelow Tump, St Weonards, Llancloudy and Welsh Newton.

Until the early nineteenth century, the road between Chepstow and Monmouth passed through St Arvans, Devauden and Trellech (the current B4293); the riverside villages of Llandogo, Brockweir and Tintern, with their associated tourism, metalworking and shipbuilding industries, were more easily accessed by river.

[9] Two turnpike houses from this period are still standing; one at St Arvans is Grade II listed, while another is by Bigsweir Bridge.

[12] The southernmost section of the A466 is the Wye Valley Link Road, which was a project built in conjunction with the first Severn Bridge.