The River Usk, (Welsh: Afon Wysg), rises in the mountains of mid-Wales then flows south-east through Abergavenny and the eponymous town of Usk to the Roman legionary fortress of Caerleon and the Bristol Channel at Newport.

It is the deepest river in the British Isles at its mouth and has the second largest tidal range in the world after the Bay of Fundy in Canada.

The Usk in history and legend
The Usk has played an important role both in the history of South Wales, and some of the local folktales. Historically, the Usk has been used as a major shipping route for much of the last millennium, mostly because of its wide and deep mouth, and good access from the Bristol Channel. Evidence of the Usk's longstanding use in transport and trade came in the form of the remains of the Newport ship which were unearthed in July 2002. The ship, dated around 1465, was most likely a trade ship, and may have been around much of Europe and beyond in its lifetime. Its presence in the Usk has only confirmed what an important trading route the Usk must have provided to the many towns and villages along its route.

The Usk has also played a role in many local and regional legends. One of the most famous legends involves King Arthur, who is thought by many to have been based in Wales. Legend has it that Arthur fought a battle against Saxon invaders near Newport and, after a victorious outcome, sailed down the Usk on a boat to Caerleon, where he held council and based himself for large stretches at a time. Some even suggest that Caerleon is the site of Camelot, though such suggestions are conjecture and are not based on any hard evidence.