Hamelin de Warenne (d. May 7, 1202) was an English nobleman who was prominent at the courts of the Angevin kings of England, Henry II, Richard I, and John.

He was an illegitimate son of Geoffrey of Anjou, and thus a half-brother of Henry II, and an uncle of Richard I and John. His half-brother Henry gave him one of the wealthiest heiresses in England, Isabella de Warenne, in her own right Countess of Surrey. She was the widow of William of Blois. Hamelin and Isabella married on in April 1164, and after the marriage he was recognized as Earl of Warenne, that being the customary designation for what more technically should be Earl of Surrey.
In consequence of the marriage Hamelin took the de Warenne toponymic, as did his descendants.

Hamelin joined in the denunciations of Thomas Becket in 1164, although after Becket's death he became a great believer in Becket's sainthood, having, the story goes, been cured of blindness by the saint's help. In 1167 he escorted his niece Joan of England to Sicily for her marriage.

He remained loyal to Henry through all the problems of the later part of the king's reign when many nobles deserted him, and continued as a close supporter of his nephew Richard I. During Richard's absence on the Third Crusade, he took the side of the regent William Longchamp. Hamelin appeared in the 2nd coronation of King Richard in 1194 and at King John's coronation in 1199.

He died in 1202 and was succeeded by his son William de Warenne, 6th Earl of Surrey. A daughter, named Adela, was the mistress of her cousin King John of England, and by him the mother of Richard Fitz Roy.