Gruffydd ap Rhys (c. 1090 – 1137) was Prince of Deheubarth, in Wales. His sister was the Princess Nest ferch Rhys. He was the father of Rhys ap Gruffydd, known as 'The Lord Rhys', who was one of the most successful rulers of Deheubarth during this period.
Gruffydd had at least two sons prior to marriage to Gwenllian:
He married Gwenllian ferch Gruffydd and by her he had issue:
Gruffydd was born in Llandeilo. Following the death of his father Rhys ap Tewdwr in 1093, Deheubarth was taken over by the Normans, and Gruffydd spent much of his early years in exile in Ireland.
In 1113 Gruffydd returned to South Wales, taking two years to gather support around him, after which, in 1115 he was accused by King Henry I of England of stirring up revolt and so went to Gruffudd ap Cynan for help. Gruffudd ap Cynan planned to murder Gruffydd to receive a reward from King Henry I, but Gruffydd's sister Nest warned him and he was able to escape to Llŷn. This was followed by the marriage of Gruffydd ap Rhys to Gwenllian ferch Gruffydd daughter of Gruffydd ap Cynan. The story goes that the two became romantically involved and eloped. She married Gruffydd ap Rhys shortly after 1116.
In 1116 Gruffydd attacked Castle Llanmyddyfri, but was defeated. He also attacked Swansea Castle, and destroyed the outer walls; and captured Carmarthen Castle, and either in this year or in 1114 captured Kidwelly Castle. However an attack on Aberystwyth was defeated and Gruffydd's army dispersed.
In 1122 Gruffydd made peace with King Henry I and was allowed to rule a portion of his father's kingdom, the Cantref Mawr, although he was soon under pressure from the Normans again and was forced to flee to Ireland for a period in 1127.
In 1135 Gruffydd was summoned by King Stephen of England to London, but refused to go. The following year he joined Owain Gwynedd and Cadwaladr, the sons of Gruffudd ap Cynan of Gwynedd, in a rebellion against Norman rule. While Gruffydd was away from home, his wife Gwenllian led her husband's troops against Maurice of London, but was defeated, captured, and beheaded. In this battle his son Morgan was also slain, and his son Maelgwn was captured. In revenge for his wife's execution Gruffydd attacked the English and the Fleming residents of South Wales, causing great destruction of property, crops, and livestock. Gruffydd himself with Owain and Cadwaladr gained a crushing victory over the Normans at Crug Mawr near Cardigan the same year. In celebration of driving the English and the Fleming from South Wales, Gruffydd hosted a grand festival that lasted for 40 days.
In early 1137 Gruffydd died in uncertain circumstances. Florence of Worcester claimed that Gruffydd was murdered by his second wife. Of course, this is impossible, since Gwenllian herself had already been executed by the English at Kidwelly Castle.
He was succeeded by his son, Anarawd. Of his other sons, Cadell, Maredydd, and Rhys (later known as The Lord Rhys) all ruled Deheubarth in turn.