John de Warenne, 8th Earl of Surrey

John de Warenne (June 30, 1286 – June 1347), 8th Earl of Surrey or Warenne, was the last Warenne earl of Surrey.

He was the son of William de Warenne, the only son of John de Warenne, 7th Earl of Surrey. His mother was Joanna, daughter of Robert de Vere, 5th Earl of Oxford.

Warenne was only six months old when his father died, and was 7 years old when his mother died. He succeeded his grandfather as earl when he was 19.

He was one of the great nobles offended by the rise of the Edward II's favorite Piers Gaveston, and help secure Gaveston's 1308 banishment. The two were somewhat reconciled after Gaveston's return the next year, but in 1311 Warenne was one of the nobles who captured Gaveston. He was however unhappy about Gaveston's execution at the behest of the earl of Warwick, which pushed him back into the king's camp.

The baronial opposition was led by the king's cousin Thomas, Earl of Lancaster, and he and Warenne became bitter enemies. Private war erupted between the two, and over the new few years Warenne lost a good part of his estates to Lancaster.

Warenne was one of the four earls who captured the two Roger Mortimers, and in 1322 he was one of the nobles who condemned to death the earl of Lancaster.

Warenne and his brother-in-law Edmund Fitzalan, 9th Earl of Arundel were the last two earls to remain loyal to Edward II after the rise to power of Queen Isabella and Roger Mortimer. After Arundel's execution he went over to the queen's side, urging Edward II's abdication in 1327.

He was the guardian of his cousin Edward Balliol, and after Balliol lay claim to the Scottish throne, accompanied him on his campaign in Lothian. Balliol created Warenne earl of Strathern, but this was in name only for the properties of the earldom were held by another claimant.

On May 25, 1306 Warenne married Jeanne of Bar, daughter of count Henry III of Bar and Eleanor, eldest daughter of king Edward I of England. The two were soon estranged and live apart, and had no children, though the marriage was never dissolved. Warenne instead took up with Matilda de Nerford, by whom he had several illegitimate children, and later with Isabella Holland, sister of Thomas Holand, later earl of Kent.

Warenne died in 1347 and is buried at the monastery of Lewes. He was succeeded as earl by his nephew Richard Fitzalan, who was also earl of Arundel.