The Prose Tristan (French: [Roman de] Tristan en prose) or Tristan de Léonois is a 13th-century Old French adaptation of the Tristan and Iseult story into a lenghty prose romance. It was the first to tie the subject entirely into the arc of the Arthurian legend, making the hero Tristan a member of the Round Table. It was also the first major Arthurian prose cycle commenced after the widely popular Lancelot-Grail (Vulgate Cycle), which influenced especially the later portions of the Prose Tristan. It exists in multiple distinct variants, notably the "short" and the "long" versions. Source: Wikipedia (en)