Red Knight is a title borne by several characters in Arthurian legend. The first is likely the Red Knight of the Heath in Chrétien de Troyes' Perceval, the Story of the Grail; he steals a cup from King Arthur and is killed by the protagonist Perceval, who wears his armor and comes to be known as the Red Knight himself. In Wolfram von Eschenbach's Parzival, a retelling of Chrétien, the Red Knight is identified as Sir Ither, and is a cousin to both Arthur and Parzival.
Two further Red Knights appear in the tale of Gareth in Sir Thomas Malory's Le Morte d'Arthur. The first is named Sir Perimones, who, like his three brothers the Black Knight, the Green Knight (distinct from the character in Sir Gawain and the Green Knight), and Sir Persant of Inde, is bested by the young Gareth. After these initial trials Gareth must face the Red Knight of the Red Launds, whose real name is Sir Ironside. Ironside has the strength of seven men and has trapped the princess of Lyonesse in a tower from which Gareth must save her. Though he had demonstrated a cruel and sadistic nature, Ironside is brought around and even made a Knight of the Round Table.
Furthermore, Gawain is also known as the Red Knight for a brief time in Perlesvaus, and Galahad is called by this name in the Lancelot-Grail cycle. In Chrétien de Troyes' story Yvain, the Knight of the Lion, the red knight Esclados guards a mystical fountain, and is defeated by Ywain.