Defender of the Vale
Defender of the Vale, alternatively Protector of the Vale, is one of the hereditary titles traditionally held by the head of House Arryn, along with Lord of the Eyrie. The Arryns rule the Vale of Arryn, which includes the Vale proper and the Mountains of the Moon.
House Arryn ruled as Kings of Mountain and Vale after the Battle of the Seven Stars in the Andal invasion. They submitted to House Targaryen during Aegon's Conquest, however, and have since served as Defenders of the Vale and Wardens of the East.