Moel Arthur ('Arthur's Hill') is an Iron Age hillfort in Flintshire, Wales, at the boundary with Denbighshire, about east of Denbigh.
It is on a prominent hill, height , in the Clwydian Range; it overlooks the Vale of Clwyd to the west. Offa's Dyke Path skirts the hill. It is about south-east of the hillfort of Penycloddiau.
The oval fort is about northâÂÂsouth and eastâÂÂwest, enclosing an area of . There are two large banks and ditches to the north, where the hill slope is not steep; above the steep south-west, south and east slopes there is a single bank. At the north-east, at the edge of the steeper slopes, there is a narrow inturned entrance with an oblique approach. The form of entrance, and the simple plan of the fort, suggest that it is an early example.
Within the fortifications, there is a rounded summit. In the north and east of the interior there is a broad terrace, and building platforms have been found.
There was excavation in 1849 by Wynne Ffoulkes. He found "coarse red Roman pottery" which has not been preserved; it is not known if it was Roman, which would suggest occupation into the Roman period, or prehistoric. He found traces of a drystone construction, destroyed during the excavation, near the south of the entrance. In 1962, three copper Bronze Age axes were found within the defences.