The Three Matters of Romance (and the Tristan/Isolde Matter)
Jean Bodel, a C12 poet and author of the Chanson des Saisnes (Song of the Saxons), wrote that there were "three matters" or topics of romance, based on the geographic location and characters in the plot: "N'en sont que trois materes a nul home entendant / De France, et de Bretaigne, et de Rome la grant."
The Matter of France--Epic and early-romance prototypes mainly based on the life of Charlemagne (Charles the Great) and his court:
Chanson de Roland (C12, based loosely on an actual event in 778); Raoul de Cambrai; Girart de Roussilon; geste de Doon de Mayence; geste de Garin de Monglane; etc. Their topics are unusually single-mindedly focused on conflicted loyalties.
The Matter of Britain--Epics and romances mainly based on the life of Arthur and his court, but eventually incorporating characters and locales from the French, German, and Roman narratives, as well:
The Celtic-Norman-English Line:
Celtic antecedents: Nennius, Historia Brittanae [History of the Britains]--"Pendragon" is a dux bellorum (duke of battle, warlord) who leads the Welsh against the Romans in 12 battles, culminating in the Battle of Mount Badon); Wawayne or Gawayne narratives built upon Nennius and the Culchallain hero-legends of Irish and Welsh Celtic tradition.
***Geoffrey of Monmouth (1100-1155), Historia Regum Britanniae c. 1136 [History of the Kings of England]: purports to be a Latin translation of a "very old Anglo-Saxon book," no trace of which has survived; establishes a chronology of Arthur's birth, kingship, and death, including the involvement of his court mage and counselor, Merlin, and Arthur's conquest of Rome to establish a Continental English Empire--no Round Table, no Lancelot, no Tristan--but this single text was the fountainhead from which all the subsequent narratives of Arthurian romance spring, with occasional infusions of new characters or matter from other traditions. If Casablanca is a plot in which "Everybody comes to Ricks," Arthurian romance is identifiable because in its plots, "Everybody comes to Arthur's [court]."
Robert Wace (1100-1175), Geste des Bretons [Deeds of the Britains], an Anglo-Norman (i.e., French) paraphrase of Geoffrey's Historia that adds the Round Table, the code of chivalry as a value system organizing Arthur's court, the tradition of knights undertaking quests or seeking adventures ("knights errant"), and emphasis on ceremonial court activity.
La3amon, Brut (c. 1205), a free translation of Wace in alliterative West Southern English that situates Arthur's kingship firmly within the English foundation myth which has the fleeing Trojan lord, "Brut," founding Londinium along the same lines that Virgil's Aeneid purported to record the foundation of Rome by the Trojan lord, Aeneas; adds description of the Round Table's origin as the queen's dowry, brought to Arthur from Ireland.
The French Line
Chretien de Troyes (1140-1191), chaplain to the court of Marie de Champagne (later wife of Henry II, king of England and France, 1154-89), living in Provence (Modern France), a series of shorter verse romances of extraordinary artistry, all set in the Arthurian past and dealing with the struggles of profane and sacred love: Erec et Enide, Le Chevalier de la Charette [Knight of the Cart, a Lancelot and Guenivere romance], and Perceval le Gallois [Perceval of Wales, an unfinished romance which introduces the Holy Grail as the object of a sacred quest for Arthur's knights].
Vulgate Cycle: an immense linked set of romances found in many Old French manuscripts from C13-15, written by many authors (spuriously} claiming to derive from original MSS sources by Robert de Boron, and developing a coherent sequential narrative of the lives and conflicts of Arthur, Guenivere, Lancelot, Gawain, Merlin, Palomides (a Saracen knight), Tristan (imported from the German tradition), and the Grail Quest, now led by Galahad, Lancelot's illegitimate son--major "branches" include the Prose Merlin, the Prose Lancelot, the Prose Tristan, the Queste del Sainte Graal, and the Mort le roi Artu.
The German Line
Thomas, Tristan (C11)
Gottfried von Strassbourg, Tristan (C13)--Gottfried takes Thomas's bare-bones story of a knight who falls in love with his lord's bride while bringing her to the wedding by adding a fatal love potion whose accidental ingestion prevents the lovers from obeying their duties as vassal and wife by overpowering their wills. This motif is borrowed to explain how Lancelot can engender Galahad on a woman who is not Guinevere. In both cases, the lady's "nurse" or "maid" is involved in the potion finding its way to the lovers' hands. The lovers are doomed by this conflicted love, leading to a romance tradition of doomed love which also works in the Lancelot-Guinevere-Arthur relationship (which also might be said to be a doomed "Arthur-Margawse-Mordred" relationship!).
Prose Tristan, C13-4, develops the bare framework of Tristan's illicit love for Isode, his uncle Mark's wife, into a vast, interlaced, multi-protagonist romance which takes Tristan to Arthur's court and establishes Mark's court as the disloyal, anti-Arthurian court in which, nevertheless, Lancelot is having an affair with Arthur's queen. The two couples exchange letters about the puzzles of their situations, a sign of later authorship, vs. earlier narratives in which they would send messengers or troubadours singing songs containing their messages.
The Middle English Line
Alliterative Mort de Arthur and Stanzaic Morte Arthure
Malory (either Kyng Arthur [Caxton, 1485] or eight separate romances like those composed by Chretien de Troyes [Works, 1947, 1967, 1997]
The Matter of Rome--Medieval adaptations of themes first found in Virgil's Aeneid about the adventures of "knights" who fled the fall of Troy and founded Rome:
Benoit de Sainte-Maure, Roman de Troie (C12)
Roman de Eneias (C13)
Roman de Thebes (C12)