The title "High King of Ireland" refers to the historical leader who held supreme authority over the various kingdoms of Ireland. This position was not a hereditary monarchy but rather a title that could be claimed by a king who had gained the support of other regional kings. The High King was often chosen during a ceremonial gathering known as the Tanistry, which involved a complex system of succession and alliances. The role of the High King diminished over time, especially after the arrival of the Normans in the 12th century. By the late medieval period, the title became largely symbolic, as local kings and chieftains gained more power. The last widely recognized High King was Rory O'Connor, who ruled in the 12th century before the fragmentation of Irish authority.