| Castell Arnallt | |
|---|---|
| Monmouthshire, Wales | |
 Site of Castell Arnallt | |
  Castell Arnallt | |
| Coordinates | 51°47′06″N 2°59′13″W / 51.785°N 2.987°W |
| Type | Castle |
| Site information | |
| Condition | Earthworks - no other visible remains |
The site of Castell Arnallt, sometimes known as Castle Arnold, is located near the village of Llanover in the Usk valley of Monmouthshire, Wales, some 4 miles (6.4 km) south east of Abergavenny. It was the fortified court house, or llys, of Seisyll ap Dyfnwal, lord of Over Gwent or Gwent Uwchcoed, before it was destroyed after Seisyll and some of his household were killed at Abergavenny Castle by William de Braose in 1175. The land is now in agricultural use, with no remains visible.