Reginald de Dunstanville (Reginald FitzRoy, Rainald), Earl of Cornwall (French: Renaud de Donstanville or de Dénestanville) (c. 1110, Dunstanville, Kent, England – 1 July 1175, Chertsey, Surrey, England), High Sheriff of Devon, Earl of Cornwall, was an illegitimate son of Henry I of England and Lady Sybilla Corbet.
Reginald had been invested with the Earldom of Cornwall by King Stephen of England, but having afterwards taken up the cause of the Empress Matilda, his sister, he forfeited his lands and honours. Around 1173 he granted a charter to his free bugesses of Triueru, and he addressed his meetings at Truro to All men both Cornish and English suggesting a continuing differentiation. He served, according to some accounts, as High Sheriff of Devon from 1173-1174.
He was buried in Reading Abbey.
He married Mabel FitzRichard, daughter of William FitzRichard (who held a number of fiefs in Cornwall) and had the following children:
He also had illegitimate children by Beatrice de Vaux, who was later married to William Brewer (justice).