Béroul in the context of "Tristan"

Tristan and Iseult, also known as Tristan and Isolde and other names, is a medieval chivalric romance told in numerous variations since the 12th century. Of disputed source, usually assumed to be primarily Celtic, the tale is a tragedy about the illicit love between the Cornish knight Tristan and the Irish princess Iseult in the days of King Arthur. During Tristan's mission to escort Iseult from Ireland to marry his uncle, King Mark of Cornwall, Tristan and Iseult ingest a love potion, instigating a forbidden love affair between them.

The legend has had a lasting impact on Western culture. Its different versions exist in many European texts in various languages from the Middle Ages. The earliest instances take two primary forms: the so-called courtly and common branches, respectively associated with the 12th-century poems of Thomas of Britain and Béroul, the latter believed to reflect a now-lost original tale. A subsequent version emerged in the 13th century in the wake of the greatly expanded Prose Tristan, merging Tristan's romance more thoroughly with the Arthurian legend. Finally, after the revived interest in the medieval era in the 19th century under the influence of Romantic nationalism, the story has continued to be popular in the modern era, notably Wagner's operatic adaptation.