thumb|200px|Arms of William de Warenne
William de Warenne, 5th Earl of Surrey (born 1160s–1170s, died 27 May 1240) was the son of Isabel de Warenne, 4th Countess of Surrey (suo jure) and Hamelin de Warenne. His father Hamelin granted him the manor of Appleby, North Lincolnshire.
Origins
Although he spent most of his life in England he was raised in Normandy.
Tournament
Based on an example letter, which was likely copied from a real letter, he was in correspondence with William de Forz, 3rd Earl of Albemarle whom he considered a great knight and whom he wanted to join his tournament team some time between 1210 and 1240. The letter reads:
:The earl of Warenne to the count of Aumale, greetings. That which ceases from use has prepared the way for its own retirement. We knights are being kept from action like unskilled clodhoppers; this long interval of sitting around, which prevents the practice of knightly exercise, gives one kidney stones. You will have heard that a certain tournament has been sworn between us and O., the earl of such-and-such a place. We beg you with our utmost affection to come to it. Since we are unfit, we trust in your integrity as to a city; to your triumphal banner as to a castle with its walls and surrounding moat, which is accustomed to be the refuge of the weary and of those oppressed by an adverse fate. And those who are accustomed to our protection in the best possible manner have committed themselves to being defended [by] the might of your protection. We also desire your presence there all the more because we believe it will be essential to us. During the king's difficulties with the barons, when they sought for the French prince to assume the English throne, William is listed as one of those who advised John to accede to Magna Carta. His allegiance only faltered a few times when the king's cause looked hopeless; shortly before the death of John, he made terms with Prince Louis. In March 1217 he again demonstrated his loyalty to England by supporting the young King Henry III, and he was also responsible for the establishment of Salisbury Cathedral. He refers to Hubert de Burgh in a letter from 1218 as his dearest friend and lord "sicut dominum et amicum carissimum".
However, he disliked the royal favorites who came into power after 1227, and used his influence to protect Hubert de Burgh when the latter had been removed from office by their efforts in 1232. Warenne's relations with the king became strained in course of time. In 1238 he was evidently regarded as a leader of the baronial opposition, for the Great Council appointed him as one of the treasurers who were to prevent the king from squandering the subsidy voted in that year. widow of Hugh Bigod, 3rd Earl of Norfolk, on 13 October 1225. They had one son, John, and a daughter, Isabel. John (1231–1304) succeeded his father as earl, while Isabel ( – 1282) married Hugh d'Aubigny, 5th Earl of Arundel. William may also have had an earlier, childless marriage to another Maud, daughter of William d'Aubigny, 2nd Earl of Arundel.