Which unfinished poem by Chrétien de Troyes contains the earliest known mention of the Holy Grail?

Chrétien de Troyes’s unfinished poem Perceval, the Story of the Grail contains the earliest known mention of the Holy Grail in medieval literature.

Written in Old French in the late 12th century, the poem follows the young Welsh knight Perceval as he enters Arthurian romance and learns the ideals of chivalry. During a mysterious procession, Perceval sees a grail carried through a castle, but Chrétien does not explain that it is the cup used by Jesus.

The poem ends before its story is resolved, probably around 1180 or the early 1190s. Later writers expanded the grail into a Christian relic associated with the Last Supper and the Crucifixion. This means the familiar holy cup is partly a later development rather than a complete feature of Chrétien’s original narrative.

The poem’s title is also translated as Perceval or the Story of the Grail, but the longer English title identifies the work most specifically.