Sibyl of Neufmarche

Sibyl de Neufmarché, Countess of Hereford, suo jure Lady of Brecknock (c. 1100 – after 1143), was a Cambro-Norman noblewoman, heiress to one of the most substantial fiefs in the Welsh Marches. The great-granddaughter of Gruffydd ap Llywelyn, king of Wales, Sibyl was also connected to the nobility of England and Normandy. Sibyl inherited the titles and lands of her father, Bernard de Neufmarché, Lord of Brecon, after her mother, Nest ferch Osbern, had declared her brother Mahel to have been illegitimate. Most of these estates passed to Sibyl's husband, Miles de Gloucester, 1st Earl of Hereford, as her dowry. Their marriage had been arranged personally by King Henry I of England in the spring of 1121. Sibyl, with her extensive lands, was central to the King's plans of consolidating Anglo-Norman power in south-east Wales by the merging of her estates with those of Miles, his loyal subject on whom he relied to implement Crown policy.

As an adult, Sibyl lived through King Stephen's turbulent reign, known to history as the Anarchy, in which her husband played a pivotal role. Following Miles' accidental death in 1143, Sibyl entered a religious life at Llanthony Secunda Priory, Gloucestershire, England, which she had endowed up to six years previously. Sibyl is buried at the priory, founded by Miles in 1136.

Sibyl was born in about 1100 in Brecon Castle, Brecon, Wales, the only daughter of Marcher Lord Bernard de Neufmarché, Lord of Brecon, and Nest ferch Osbern. Nest was the daughter of Osbern FitzRichard and Nest ferch Gruffydd. Sybil's maternal great-grandparents were Gruffydd ap Llywelyn, king of Wales, and Ealdgyth (Edith of Mercia). Ealdgyth, the daughter of Ælfgar, Earl of Mercia, was briefly Queen consort of England by her second marriage to Harold Godwinson, the last Anglo-Saxon king of England, who was killed at the Battle of Hastings.