King of Ireland, husband of Queen Isolde, and father of Isolde in Gottfried’s Tristan.
As a bitter enemy of King Mark of Cornwall, he sent his best knight, Morholt, to menace Cornwall and collect a tribute. Tristan traveled to Ireland under the name ‘Tantris’ and killed a dragon. When Gurmun learned of this noble deed – and then of Tristan’s true identity – he agreed to peace between Ireland and Cornwall and he gave his daughter to Mark.
Gottfried says that Gurmun’s father was the King of Africa. The name probably comes from Gormund who, in Geoffrey, was an African king who conquered and established himself in Ireland.
His character in other romances is called Anguish.
Source
Tristan | Gottfried von Strassburg, early 13th century