Penhow (Welsh: Pen-h ) is a small village and community parish just inside the eastern edge of the boundary of the city of Newport, South Wales, within the historic county of Monmouthshire. The name Penhow was believed to be derived from the Welsh word Pen and How derived from the Old Norse word Haugr meaning hill or mound.Penhow is best known for Penhow Castle, which has claims to be the oldest inhabited castle in Wales. It was built as a home for Sir Roger de St Maur, one of the Norman knights who served the Norman Lord of Striguil at Chepstow Castle. He built a tower house, and documentary evidence shows that he was at Penhow by 1129.