The Castle of Dinerth (, also Castell Allt Craig Arth) is a Welsh castle located near Aberarth, Ceredigion, west Wales (ca.1110). The ruins of the medieval timber castle can be found on a hill about 1½ miles up the valley from the seaside town of Aberarth. The founder is thought to be one Richard de la Mare, a follower of Richard Fitz Gilbert, Lord of Clare, an Anglo-Norman lord, who, by the archaeological evidence, built it on top of a previous defensive position.