The "Lais of Marie de France" is a collection of twelve narrative poems (in a specific form called a 'lay') that were written at some point in the 12th century. They are primarily concerned with the theme of love and courtliness, and as such the heroes are usually knights or aristocratic ladies. While Marie makes little attempt to present a coherent message through the poems – in truth, each poem considers a different element of love and life – certain themes do resonate throughout.
Marie begins with a "Prologue" in which she states her reason for composing the lays, and confesses her hope that her audience will enjoy the work.
"Guigemar" tells of a knight who has no interest in love until he is cursed by a magical deer who says he will never be healed until he finds a woman for whom he pines. Guigemar finds a magic boat that takes him across the sea, where he falls in love with a woman married to an oppressive lord. When the lord discovers their relationship, he banishes Guigemar, who leaves his lady behind and is heartbroken as a result. They are later reunited when the lady takes the magical boat to his land and Guigemar rescues her from the lord who finds her and keeps her captive.
"Equitan" tells of a king who has an affair with his seneschal's wife, and plots with the wife to kill the seneschal. Their plan goes awry when the seneschal finds them in each other's arms, at which point both villains die by the same plot they'd intended to kill the seneschal.
"Le Fresne" tells of a young twin girl given away by a mother who fears she will be scorned for birthing twins. The girl is raised in an abbey, growing into a noble and selfless young woman who begins an affair with the lord of the land. When the lord is forced to take a wife and unknowingly marries Le Fresne's birth sister, Le Fresne shows great kindness towards them by offering the tokens her mother had bequeathed her, thereby revealing her true identity and announcing herself worthy of marriage with her beloved.
"Bisclavret" is the story of a knight who suffers from a werewolf curse, and his wife who, disgusted by the secret, plots with her lover to keep Bisclavret stuck in wolf form. Long after, the king finds and comes to love the wolf, who is docile until he encounters the wife and lover, whom he attacks. The king realizes the truth, and Bisclavret is brought back to human form and rewarded.
"Lanval" tells of a good but unpopular knight in King Arthur's court who begins an affair with a magical, extremely beautiful, maiden. When he resists the advances of the Queen and boasts that his lady dwarfs her in beauty, Lanval is put on trial for insulting the Queen and faces certain punishment unless his lady appears to validate his claim. She ultimately arrives, and they leave together for a distant land.
"Les Deus Amanz" tells of a father who keeps his daughter from marriage unless a suitor can carry her in his arms up an enormous mountain, and the young boy who swears to win the challenge. The girl and boy concoct a plan whereby the boy will take a strength potion to help him persevere, but his vanity takes over in the heat of the moment and though he does get her to the mountaintop, he dies immediately, and she follows him to death from heartbreak.
"Yonec" tells of a wife kept hidden in a tower by an oppressive husband, and a magical knight who visits her in the form of a hawk. When the knight is mortally wounded by a trap left by the cuckolded husband, he promises his love before dying that she is pregnant and that their child will avenge his death. Much later, the child, Yonec, learns the truth and kills the step-father.
"Laüstic" tells of a woman in a loveless marriage, and the unconsummated affair she holds with the knight who lives next door. They stand each night beholding one another from their windows, until the husband grows suspicious and she tells him she awakens to listen to the nightingale. He has the bird killed, and she sends it to the neighbor, who wears it around his neck as symbol of their love and tragedy.
"Milun" tells of a knight famous for his jousting ability, and his long relationship with a woman whom he cannot have, at first because she grows pregnant and they must give away the child, and later because she is given in marriage to another. They maintain a decades-long relationship by sending messages and meeting occasionally. Meanwhile, their son grows to be a very talented knight in his own regard, gaining a great reputation as he seeks his father. Milun grows jealous of this new knight's fame, and sets out to joust him. The son bests the father, but they recognize one another and are happily joined. The woman's husband meanwhile dies of his own accord, and the family is reunited.
"Chaitivel" tells of a beautiful woman who refuses to choose a suitor because she loves the attention. When her four most accomplished suitors are attacked after a successfully aggressive tournament, and all but one are killed, she spends the rest of her life nursing the wounded survivor and ruing her losses.
"Chevrefoil" is an episode from the Tristam and Isolde legend. In this episode, Tristam, who has been banished by his king uncle because of his love for the queen, waits on a path as the queen's escort passes. The queen sees a sign he left and sneaks away, where they enjoy their brief happiness before she must leave again.
"Eliduc" tells of a knight in a happy marriage who is banished when the king believes some false claims about him. Overseas, Eliduc falls in love with the daughter of his new lord, but refuses to consummate the relationship out of loyalty to his wife. When he is called back home to defend his old lord, his wife sees his sadness. He returns to claim the young woman from overseas, but on the trip back to his homeland, she learns of his wife and falls into a swoon, seemingly dead. He keeps her in a removed hermitage, where his wife ultimately finds her and brings her back to life. The wife pledges to be a nun so her husband and his beloved might marry, but all three ultimately end up giving their lives to God.