William III de Beauchamp (c. 1215 – 1269[1]) of Elmley Castle in Worcestershire, was an English Baron and hereditary Sheriff of Worcestershire.
He was the son and heir of Walter II de Beauchamp (1192/3-1236) of Elmley Castle, hereditary Sheriff of Worcestershire, by his wife Johanna Mortimer (d.1225), daughter of Roger Mortimer (d. 1214) of Wigmore Castle in Herefordshire.
On the death of his father in 1236 he became hereditary Sheriff of Worcestershire, which title he held until his death. In 1249 he was excommunicated by Walter de Cantilupe, Bishop of Worcester, but was later absolved, in the presence of the king, on St. Edmund's Day, 1251.[2]
He married Isabel de Mauduit, daughter of William de Mauduit of Hanslope in Buckinghamshire and Hartley Mauditt, Hampshire (by his wife Alice de Beaumont (d. pre- 1263), half-sister of Henry de Beaumont, 5th Earl of Warwick[3] (c.1192-1229)) and sister and heiress of William Mauduit, 8th Earl of Warwick. By Isabel he had issue including: