River Honddu (Monmouthshire)
River Honddu, or Afon Honddu in Welsh, is a river in southeast Wales. It runs through the Black Mountains in the Brecon Beacons National Park and is about 24 kilometers long. It starts near Gospel Pass in Powys, flows south into Monmouthshire past Llanvihangel Crucorney, then turns northeast to join the River Monnow near the Wales–England border.
Its main tributary is Nant Bwch; many smaller streams feed the Honddu as it travels down the Vale of Ewyas.
The upper valley has a U-shaped, glacial look, showing that ice once carved this landscape. Today the Honddu is a “misfit river” because the ice did deeper work than the river does now. The river’s path may reflect ancient geological faults, such as the Neath Disturbance.
In the valley you can visit Llanthony Priory. At the lower end is Cwmyoy, a village known for its church perched on a hillside that has moved on a landslide.
The Welsh name is Afon Honddu, pronounced hon-thee.
This page was last edited on 1 February 2026, at 14:25 (CET).