William de Hereford was a holder of the feudal lordship of Abergavenny in the Welsh Marches in the mid twelfth century.
William de Hereford was a son of Miles de Gloucester, 1st Earl of Hereford and his wife Sybil de Neufmarche, daughter of Bernard de Neufmarche of Brecon.
His brothers were Mahel de Hereford and Walter de Hereford.
He was made King's Constable of the region and succeeded to the title of Baron Abergavenny circa 1164.
William de Hereford died as a result of injuries sustained from falling masonry during a fire at Bronllys Castle near modern Talgarth, Powys in 1166. He died without issue.