The King of Ulster (, ) 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