Elaine is best known as the unrequited lover of Lancelot, though another Elaine (also known as Helen), was the mother of Lancelot and wife of King Ban of Brittany who after the death of her husband and the loss of her baby son Lancelot, who is stolen by the Lady of the Lake, takes the veil. The first Elaine is described by Malory in his story "The Fair Maid of Astolat." Elaine falls hopelessly in love with Lancelot when he visits her home before a joust. He is wounded in the tournament and Elaine nurses him to health, then proposes to Lancelot, who gently refuses her, saying he has vowed never to be a wedded man. Then Elaine asks, "Then, fair knight, will ye be my paramour?" a request Lancelot also refuses. Elaine concludes that she must die if she cannot have the love of Lancelot. Lancelot then offers to give her a thousand pounds yearly is she "will beset (her) heart upon some good knight." Elaine vows she will never marry another and asks her father to place her corpse in a barge and set it upon the Thames. Tennyson in his poem "The Lady of Shalott" echoes many of the themes of the medieval Elaine story, perhaps unconsciously as he claimed he had not read the story in Malory before composing his poem.

In other versions, Elaine and Lancelot are the parents of Galahad, the purest knight of Arthur's court and the one who finally attains the Grail. This is Elaine of Pelles, described by Malory in Part Five: Sir Tristram of Lyoness, Chapt XIV, Sir Lancelot and Elaine. The enchanted Lancelot sleeps with this Elaine, believing she is Guinevere. Elaine of Pelles had herself been confined in a tower by Morgan le Fay and the Queen of North Wales because of her beauty. She was not to leave the tower until "the best knight in the world would take her by the hand." Lancelot is this knight who rescues Elaine from the tower.