A late 14th-century verse romance in alliterative verse usually ascribed to the Pearl-Poet, because it is preserved in the same manuscript (Ms. Cotton Nero A x) as Cleanness, Patience and Pearl. The poem is 2,530 lines long and is divided into four sections of approximately equal length. The stanzas are, however, of unequal length ending with a bob and wheel.
The poem's story is set in the days of King Arthur. The New Year's feast at Camelot is disturbed by a huge green knight who challenges any member of the court to deal him a blow that is to be returned at his home, the Green Chapel, twelve months later. Sir Gawain beheads the knight, who picking up his head reminds Gawain of the bargain and leaves. At Michaelmas, Gawain sets off for the Green Chapel. On Christmas Eve, he is invited by Sir Bertilak to stay at his castle which is close to the Chapel. The host and Gawain agree to exchange each evening what they have gained during the day. The host goes hunting and Gawain has to resist the temptations of the seductive Lady Bertilak. On the third day he fails, because he does not present the lady's gift, a magic green girdle which makes him invulnerable. At New Year, Gawain rides to the chapel meeting the green knight who cannot cut off Gawain's head because of the magic girdle. The knight reveals to him that he is Sir Bertilak and that the whole episode was planned by Morgan le Fay. Ashamed Gawain returns to Arthur's court. The other knights say that from now on they will wear a green girdle as a token of sympathy.