The King of Ulster (Old Irish: Rí Ulad, Modern Irish: Rí Uladh) also known as the King of Ulaid and King of the Ulaid, was any of the kings of the Irish provincial over-kingdom of Ulaid. The title rí in Chóicid, which means "king of the Fifth", was also sometimes used.
Originally referring to the rulers of the Ulaid of legend and the vastly reduced territory of the historical Ulaid, the title rí Ulad ceased to exist after the Norman invasion of Ulaid in 1177 and the subsequent foundation of the Earldom of Ulster. The Mac Dúinnshléibe dynasty of Ulaid (English: Donleavy / Dunleavy) were given the title of rex Hibernicorum Ulidiae, meaning "king of the Irish of Ulaid", until the extinction of their dynasty by the end of the 13th century.
After the earldom's collapse in 1333, the title was resurrected and usurped after 1364 by the Ulaid's chief Gaelic rivals the Northern Uí Néill, who had overrun the ruins of the earldom and established the renamed tuath of Clandeboye. The Northern Uí Néill had achieved dominance over the north of Ireland, with their territory corresponding largely to the modern day province of Ulster. The title thus came to apply to their territory, which they likewise renamed Ulaid, now reflecting an area roughly corresponding to the extent of Ulaid in legend. "Prince of Ulster" became a common title for The O'Neill (In Irish: Ui Neill) until the Flight of the Earls in 1607.
Legendary kings
Eber Donn
Cimbáeth
Macha Mong Ruad
Fergus mac Léti
Congal Cláiringnech
Ross Ruad
Eochaid Sálbuide
Fergus mac Róich
Conchobar mac Nessa
Cúscraid mac Conchobar
Fíatach Finn
Éllim mac Conrach
Mal mac Rochride
Tipraiti Tireach
Áengus Goibnenn mac Fergus Gallen mheic Tibraide Tirech
Fergus Dubdétach
Aengus Finn mac Fergus Dubdétach
Lugaid Lorc mac Áengus Finn
Dub mac Fomor mheic Airgetmar
Fiachu Araide mac Áengus Goibnenn mheic Fergus Gallen
Fedlimid mac Cas mheic Fiachu Araide
Imchad mac Fedlimid
Ros mac Imchad
Cronn Badruí mac Eochaid mheic Lugaid mac Ros mac Imchad
Fergus Foga mac Fraechar Foirtriun
Cáelbad mac Cronn Badruí
Sárán mac Cóelbad
Mihail
Historic kings
Cumhscraid I, King of Ulster (-38)
Cumhscraid II, King of Ulster (-48)
Glaisne King of Ulster (-60)
Irial King of Ulster (48-100)
Fiachadh, King of Ulster (74-120)
Elim King of Ulster (95-130)
King Mal of Ulster (111-164)
Breasal King of Ulster (130-183)