The River Usk (/ʌsk/; Welsh: Afon Wysg) rises on the northern slopes of the Black Mountain (y Mynydd Du), Wales, in the westernmost part of the Brecon Beacons National Park.

Its flora and fauna are diverse and include Atlantic salmon, European otters, twait shad, shad, lamprey, European perch, brown trout, chub, common dace and common roach as well as kingfishers, grey herons and other wildfowl and bird life.

A number are of historic interest, notably a series of largely eighteenth and nineteenth century listed structures between Abercamlais and Newport.

The highest crossing is that of Pont ar Wysg (translates from Welsh as bridge on the Usk) which carries the moorland road west from Trecastle to Twynllanan.

There are a further couple of minor road crossings below the Usk Reservoir dam around Cwmwysg, then Pont Newydd (translates as new bridge) immediately south of Trecastle.

[8] The Grade I listed Usk Bridge in Brecon dates back to 1563 but it was significantly altered in the 1950s to accommodate increased road traffic.

It is supplemented by a modern concrete span bridge carrying the A40 Brecon bypass dual carriageway over the river to the east of the town.

A couple of private footbridges span the next section of the river before its waters pass beneath the historic (grade I listed) Llangynidr Bridge.

A private footbridge spans the river at Llanover and the mainline railway crosses it at The Bryn, a small village otherwise known as Llangattock Nigh Usk.

A long unbridged section follows until, just upstream from the normal tidal limit on the Usk, it is crossed by the Grade II* listed New Bridge at Newbridge-on-Usk, probably also a legacy of Edwards from 1779.

The innovative Newport City footbridge was opened in 2006 to carry both pedestrians and cyclists over the river as part of an urban regeneration project.

[16] Forge Mill north of Bettws Newydd at SO 355974 was still in use at the end of the nineteenth century, using a 200m long weir stretching between islands on the river to draw its water.

[19] In addition to these there is an enigmatic leat beside the uppermost section of the river's course which is presumed to have drawn water off it at SN 816263 and transferred it via a contouring route across the moors for over 2 km.

The Medieval Latin text De Ortu Waluuanii recounts a humorous tale in which an incognito Gawain pushes his uncle King Arthur into the Usk, and is then forced to explain to his wife Gwendoloena (Guinevere) why he is so wet.

[22] Geoffrey of Monmouth writes of Caerleon in the mid 12th century: For it was located in a delightful spot in Glamorgan, on the River Usk, not far from the Severn Sea.