High Quality Content by WIKIPEDIA articles! Rhys ap Gruffydd or ap Gruffudd (Anglicised to "Griffith") (1132 – 28 April 1197) was the ruler of the kingdom of Deheubarth in south Wales. He is commonly known as The Lord Rhys, in Welsh Yr Arglwydd Rhys, but this title may not have been used in his lifetime. He usually used the title "Proprietary Prince of Deheubarth" or "Prince of South Wales", but two documents have been preserved in which he uses the title "Prince of Wales" or "Prince of the Welsh". Rhys was one of the most successful and powerful Welsh princes, and after the death of Owain Gwynedd of Gwynedd in 1170 was the dominant power in Wales.