Isabel de Forz, 8th Countess of Devon

Isabel de Forz (or Isabel de Redvers, Latinized to Isabella de Fortibus; July 1237 – 10 November 1293) was the eldest daughter of Baldwin de Redvers, 6th Earl of Devon (1217–1245). On the death of her brother Baldwin de Redvers, 7th Earl of Devon, in 1262, without children, she inherited suo jure (in her own right) the earldom and also the feudal barony of Plympton in Devon, and the lordship of the Isle of Wight. After the early death of her husband and her brother, before she was thirty years old, she inherited their estates and became one of the richest women in England, living mainly in Carisbrooke Castle on the Isle of Wight, which she held from the king as tenant-in-chief.

She had six children, all of whom died before her. On her death bed, she was persuaded to sell the Isle of Wight to King Edward I, in a transaction that has ever since been considered questionable. Her heir to the feudal barony of Plympton was her cousin Hugh de Courtenay, 1st/9th Earl of Devon (1276–1340), feudal baron of Okehampton, Devon, who in 1335 was declared Earl of Devon.

Countess Wear, now a suburb of Exeter, is named after a weir that she built on the River Exe, and she is the subject of several legends and traditions.

She was the eldest daughter of Baldwin de Redvers, 6th Earl of Devon (1217–1245), of Tiverton Castle in Devon, by his wife Amice de Clare (c. 1220 – 1284), a daughter of Gilbert de Clare, 4th Earl of Hertford, 5th Earl of Gloucester, 1st Lord of Glamorgan. Her early life was apparently spent at Tidcombe near her father's seat at Tiverton.

At the age of 11 or 12 she became the second wife of William de Forz, 4th Earl of Albemarle (died 1260), who held land in Yorkshire and Cumberland and was Count of Aumale in Normandy. When he died in 1260, their children were minors, so the wardship of his heir (whose name is not known), and his estates passed to the crown, namely King Henry III. One-third of her late husband's estates were granted to Isabel as her dower, comprising one-third of the feudal barony Holderness, half of the feudal barony of Cockermouth, and the feudal barony of Skipton. She was also granted custody of two of her younger sons, Thomas and William. The king granted to his own son and heir apparent, Prince Edward (later King Edward I), the other two-thirds of the estates and the marriage of the heir.

She had six children by William de Forz, four sons and two daughters, who all predeceased her:

Upon her father's death. Marrying William de Forz.

After his death she courted: