William FitzGeoffrey de Mandeville (died 1227) was the third Earl of Essex of the second creation from either 1219 or 1216 until his death.

During the barons war he laid siege to Berkhamsted castle in the month of December 1216, attempting to take it from the castellan Waleran the German.

He must have reconciled with the royal government of Henry III because by 1220 he complained to the royal administration that his market rights in the town of Moretonhampstead were being infringed upon by Hugh de Chaggeford who was the lord of Chagford which held its own market.

[2] The outcome of the case is unknown but there isn't any indication that de Chagford's event was disbanded.

[2] He was married to Christina, one of Robert FitzWalter's daughters, but died on 8 January 1227, without heirs and the earldom became extinct.