Sir Agravain or Sir Agravaine is a nephew of King Arthur and a Knight of the Round Table in Arthurian legend. He is the second son of King Lot of Orkney and Lothian and Morgause, full brother to Gawain, Gaheris and Gareth. His half-brother and most frequent associate in the Post-Vulgate Cycle is Mordred. His mother's parents were Gorlois and Igraine; she was a sister of Elaine and Morgan le Fay and maternal half-sister to King Arthur.
Agravain is described as handsome and a capable fighter, but unlike his heroic brothers Gawain and Gareth, Agravain has a reputation for malice and villainy. He plays an important role in most cyclical Arthurian literature, from the Vulgate Cycle to Malory's Le Morte d'Arthur when he exposes his aunt Guinevere's affair with Lancelot. Though Gawain, Gaheris and Gareth try to stop them, he and Mordred conspire to catch the adulterers together. In some versions he is killed by the escaping Lancelot, in others he dies defending Guinevere's execution from Lancelot's forces along with Gaheris and Gareth. In either case, it is not his death but Gaheris' and Gareth's that inspires Gawain's wrath toward Lancelot, as Gawain had warned Agravain not to spy on Lancelot.
Throughout the stories Agravain participates in acts of villainy such as the murders of Sir Lamorak and Sir Dinadan, but sometimes his acts are not so malignant. He participates in a number of adventures early in the Vulgate Cycle, and sometimes even does heroic deeds. In Sir Gawain and the Green Knight where he is called "Agravain of the Hard Hand" he is named in a list of respectable knights; this combined with his unobjectionable depiction in Chrétien de Troyes' Perceval suggests his reputation might not have been so villainous prior to the Vulgate.
In modern Arthuriana, his characterization has only gotten worse. In his poem "The Defence of Guenevere," the Victorian pre-Raphaelite poet William Morris describes Agravain as the murderer of his mother. In The Once and Future King by T. H. White, it is again Agravain, not Gaheris as in Malory, who murders their own mother, in addition to being the "bully" of the family, and killing a unicorn in their childhoods. In that work he is a drunken, bloodthirsty coward, though intelligent and not altogether unsympathetic. In the BBC's Merlin, he is Arthur's villainous uncle, appearing to want to guide the prince after his father become incapacitated, while secretly working with Morgana to try and bring Arthur down and return her to the throne, presumably out of revenge for the death of his sister and brother at King Uther's hands.
Conversely, the 1995 movie First Knight (starring Richard Gere as Lancelot) depicts Agravaine as heroic; he is portrayed by Liam Cunningham. This is the result of a strange anomaly in Malory; though always depicted as an outspoken enemy of the Queen, Agravaine is nonetheless chosen as one of her knights when she rides out on May Day (a journey that begins the episode dealt with in the film).