Iowerth Goch ap Maredudd (c.1110 - c.1171), a minor Prince and nobleman of the Kingdom of Powys, was the illegitimate son of Maredudd ap Bleddyn and Cristin ferch Bledrus. The appellation "Goch", meaning red, probably referred to the colour of his hair. Iowerth married Maud de Manly, who gave him two sons, Gruffydd Vychan (c.1150), and Hywell ap Iowerth He had one brother Hywel ap Maredudd and two half-brothers, Madog ap Maredudd and Gruffydd ap Maredudd. Iowerth is known to have taken Tomen y Rhodwydd, Llandegla, Denbighshire (a castle built by Owain Gwynedd in 1149) in 1157 and burnt it down.