Tristan (Latin/Brythonic: Drustanus; Welsh: Trystan), also known as Tristram or Tristain and similar names, is the hero of the legend of Tristan and Iseult. In the legend, he is tasked with escorting the Irish princess Iseult to wed Tristan's uncle, King Mark of Cornwall. Tristan and Iseult accidentally drink a love potion during the journey and fall in love, beginning an adulterous relationship that eventually leads to Tristan's banishment and death. The character's first recorded appearance is in retellings of British mythology from the 12th century by Thomas of Britain and Gottfried von Strassburg, and later in the Prose Tristan. He is featured in Arthurian legends, including the seminal text Le Morte d'Arthur, as a skilled knight and a friend of Lancelot.

The historical roots of Tristan are unclear; his association with Cornwall may originate from the Tristan Stone, a 6th-century granite pillar in Cornwall inscribed with the name Drustanus (a variant of Tristan). He has been depicted in numerous historical and modern works of literature, music, and cinema. Richard Wagner's influential 19th-century opera Tristan und Isolde portrays Tristan as a doomed romantic figure.