(Rhiwabon), a town of Denbighshire, N. Wales, in the E. parliamentary division, near the Shropshire border, 5 m. S. W. of Wrexham, on the Great Western railway. Pop. (1901) 3248. It is situated on a small tributary of the Dee. The old Gothic church is thought by some to have been founded by Mabon, a brother of Llewelyn (13th c.), and has monuments to the Wynn family, by Nollekens and Rhysbrac, and to Dr D. Powel (d. 1598), translator into English of Caradoc's (of Llancarfan) History of Wales. In the neighbourhood are collieries, engineering works, an iron foundry and chemical works, besides an extensive industry in glazed and other bricks. Near Ruabon is Caerdden (Caerddin), an ancient camp (village) surrounded by circular intrenchments, and Wynnstay, with an avenue of fine trees. Anciently the residence of Madoc ab Gruffyd Maelor (founder of Valle Crucis Abbey), it was called Wattstay, from Watt's Dyke, an old rampart on the estate. It was named Wynnstay on its coming into possession of the Wynns (17th c.). Offa's Dyke, near here, is io ft. high, and broad enough for two carriages abreast. Not far is Chirk Castle (supposed to have been built in 1013), besieged by Cromwell's artillery: near it, in the Ceiriog valley, the defeat of Henry II. by Owen Gwynedd took place in i 165.