Chrétien de Troyes’s Perceval, le Conte du Graal was probably composed in the 1180s.
The poem is generally dated to the late 12th century, most often around 1180–1190. Chrétien began writing it for Philip, Count of Flanders, but died before completing it. The unfinished romance introduced a mysterious grail-bearing procession during Perceval’s adventures.
The work is important because it is the earliest surviving literary text to connect a grail with the Arthurian world. Chrétien does not clearly identify the object as the cup from the Last Supper, and his poem leaves its meaning partly unexplained.
Later writers expanded the story dramatically, linking the Grail with Joseph of Arimathea, Christian relic traditions, and a formal quest. The precise year is unknown, so the decade—not a single year—is the safest conventional answer.