Rhodri ap Merfyn (c. 820 – 873), also known as Rhodri the Great, became King of Gwynedd in 844 and later Powys and Seisyllwg. In various histories, he was referred to as the King of Wales. He was the husband of Angharad ferch Meurig, with whom he formed a unified and savvy leadership.
Born around 820 as the son of Merfyn Frych, Rhodri ascended to the throne of Gwynedd in 844 following his father's death. Through his marriage to Angharad ferch Meurig, a princess of Seisyllwg, Rhodri eventually came to assimilate the numerous Welsh kingdoms under his rule. By 872, his kingdom largely comprised of what is now modern-day Wales and he was given the title of King of the Britons.
As King of the Britons, Rhodri spent much of his reign defending the borders of his kingdom, often clashing against the Kingdom of Mercia in Western England. Following the Viking invasion, Rhodri also came to clash against the Viking invaders, and at one point, developed a bitter feud with the Viking leader Ivarr the Boneless. During one such encounter, Rhodri fought against Ivarr and left a prominent scar on the Viking's face.
Personality and characteristics
Rhodri was a robust and authoritarian king who would not hesitate to use violence against his enemies, especially against his nemesis Ivarr the Boneless, whom he detested with all his soul.  Despite being a devout Christian and faithful to his religion, he resorted to divination to know his fate, and all his seers predicted that he would die at the hands of a dragon. 
Behind the scenes
Rhodri's date of death has been a subject of much debate. The Brut y Tywysogion records his death occurring at the Battle of Sunday on Anglesey in 873, while the Annales Cambriae has the two events occurring in different years. Egerton Phillimore recorded his death as 877 in his article Y Cymmroder. The Anglo-Saxon Chronicle states that Rhodri and his brother Gwriad were killed in battle against the Mercians in 878.