In Arthurian legend, Morholt (also called Marhalt, Marhault, Morold, Marhaus and other variations) is an Irish warrior who demands tribute from King Mark of Cornwall until he is slain by Tristan, Mark's nephew and defender. He appears in almost all versions of the Tristan and Iseult story, beginning with the verse works of Thomas of Britain and Béroul. The authors of later romances expanded the Morholt's role; in works like the Prose Tristan, the Post-Vulgate Cycle, and Thomas Malory's Le Morte d'Arthur, he is a Knight of the Round Table before his fateful encounter with Tristan. In many versions, Morholt's name is prefaced with a definite article (i.e., The Morholt) as if it were a rank or a title, but scholars have found no reason for this.
In the early material, Morholt is the brother of the Queen of Ireland and the uncle of Tristan's future love (both mother and daughter are named Iseult). He comes to Cornwall to collect tribute owed to his country, but Tristan agrees to battle the champion on the remote Saint Samson's Isle in order to release his people from the debt. Tristan mortally wounds Morholt, leaving a piece of his sword in the Irishman's skull, but Morholt stabs him with a poisoned spear and escapes to Ireland to die. The injured Tristan eventually travels to Ireland incognito to receive healing from the Iseult the Younger, but is found out when the queen discovers the piece of metal found in her brother's head fits perfectly into a chink in Tristan's blade.
The prose romances add many more details to Morholt's career; the Post-Vulgate and Malory record his adventures with the young Gawain and Ywain early in King Arthur's reign. In the later versions, Tristan takes Morholt's place at the Round Table when he joins the company himself.