Rhys ap Gruffydd or ap Gruffudd (often anglicised to "Griffith") (1132 – 28 April 1197) was the ruler of the kingdom of Deheubarth in south Wales from 1155 to 1197. Today, he is commonly known as The Lord Rhys, in Welsh Yr Arglwydd Rhys, although this title may have not been used in his lifetime. He usually used the title "Proprietary Prince of Deheubarth" or "Prince of South Wales", but two documents have been discovered 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, the dominant power in Wales.