Sir Calogrenant, sometimes known in English as Colgrevance, or, in ancient Welsh, Cynon ap Clydno, is a Knight of the Round Table in Arthurian legend. He is a cousin to Sir Ywain, and his courtesy and eloquence were known throughout the kingdom.
Calogrenant first appears in Chrétien de Troyes' Yvain, the Knight of the Lion. After a good meal, Calogrenant tells a story to a group of knights and Queen Guinevere about an adventure he had in the forest of Brocéliande. He had heard of a magic spring in those woods which could create a huge storm whenever someone poured its water into a nearby basin. With directions from a local family and a gruesomely depicted giant, Calogrenant reached the spring and summoned the storm. Immediately after the storm, a knight named Esclados attacked him for causing such havoc. The knight soundly defeated Calogrenant, but didn't kill him. Calogrenant's cousin Ywain is upset that Calogrenant never told him of this defeat, and sets out to avenge him, embarking on the adventure that sets up the remainder of events in the romance.
Calogrenant appears later in the Lancelot-Grail Cycle as an excellent knight, though his kinship to Ywain is not as clear as in Chrétien. He dies during the Grail Quest while trying to keep Sir Lionel from killing his own brother, Bors. Bors had faced a dilemma over whom to rescue between Lionel, who was getting beaten with thorns by two rogue knights, and a maiden who had just been abducted, and chose the maiden over his brother. Lionel was not pleased by this, and attacked Bors the next time he saw him. A religious hermit tried to intervene, but was killed accidentally in the process, and Calogrenant stepped in. Bors would not fight his brother, and Lionel slays Calogrenant and goes after Bors until God steps in and renders him immobile.
Thomas Malory recounts Calogrenant's death scene in his Le Morte d'Arthur, but also includes another one later in the narrative. Despite dying on the Grail quest, he turns up as one of the twelve knights who help Agravaine and Mordred trap Lancelot and Guinevere together. Lancelot has no armor or weapons, but he pulls Colgrevance into the room and kills him, and uses his sword to slay the rest of the company (though Mordred escapes).
Roger Sherman Loomis and others speculated that Calogrenant was used specifically as a foil for Sir Kay in some lost early version of the Yvain story. In Chrétien's romance he is presented as everything Kay is not: polite, respectful, and well-mannered. By this theory, his name can be deconstructed to "Cai lo grenant", or "Cai the grumbler", which would represent another opposite characteristic of Kay, who was famous for his acid tongue.
Calogrenant appears in the Welsh Romance Owain, or the Lady of the Fountain as Cynon, known elsewhere in Welsh tradition as the lover of Owain's sister Morvydd. Cynon is stated to be the son of Clydno, possibly connected to Clyddno Eiddin.