The Lancelot-Grail Cycle, also known as the Vulgate Cycle or the Pseudo-Map Cycle, is an early 13th-century French Arthurian literary cycle consisting of interconnected prose episodes of chivalric romance originally written in Old French. The work of unknown authorship, presenting itself as a chronicle of actual events, retells the legend of King Arthur by focusing on the love affair between Lancelot and Guinevere, the religious quest for the Holy Grail, and the life of Merlin. The highly influential cycle expands on Robert de Boron's "Little Grail Cycle" and the works of Chrétien de Troyes, previously unrelated to each other, by supplementing them with additional details and side stories, as well as lengthy continuations, while tying the entire narrative together into a coherent single tale. Its alternate titles include Philippe Walter's 21st-century edition Le Livre du Graal.

As a literary genre, the chivalric romance is a type of prose and verse narrative that was popular in the noble courts of high medieval and early modern Europe. They were fantastic stories about marvel-filled adventures, often of a chivalric knight-errant portrayed as having heroic qualities, who goes on a quest. It developed further from the epics as time went on; in particular, "the emphasis on love and courtly manners distinguishes it from the chanson de geste and other kinds of epic, in which masculine military heroism predominates."