Blestium was a small fort and iron working centre in the Roman province of Britannia Superior, part of Roman Britain. It has been identified with the site of the later town of Monmouth in south east Wales, located adjoining the confluence of the River Monnow with the River Wye. A plaque on the local bank records its position.

Monmouth is a market town and community in Monmouthshire, Wales, situated on where the River Monnow joins the River Wye, two miles from the Wales–England border. The population in the 2011 census was 10,508, rising from 8,877 in 2001. Monmouth was the county town of historic Monmouthshire, although Abergavenny is the largest settlement and Monmouthshire County Council has its main offices at Rhadyr, just outside Usk. Monmouth is in the Monmouth UK Parliament and Senedd constituencies.