Isabella of Gloucester was born circa 1160 as the third and youngest daughter William, Earl of Gloucester and his wife, Hawise. Her father was a first cousin of King Henry II as the son of Robert of Gloucester, the Empress Mathilda’s illegitimate half-brother. Unfortunately, despite her famous relations, nothing is recorded of her childhood. In 1166, Isabella’s only brother died, and this left Isabella and her sisters as co-heiresses to their father’s estate. Her father was anxious to keep the estate together, and in 1176 he entered into an agreement with King Henry II. Isabella was made William’s sole heiress, and she was to marry the King’s youngest son John. Meanwhile, her sisters were compensated with an income.
Isabella’s father died on 23 November 1183, and she became a ward of King Henry II. Instead of insisting on the marriage, he took the Gloucester income for himself. King Henry II died in July 1189 and was succeeded by his son, now King Richard I. Later that year, Isabella and John were finally married. By then she was nearly 30, and she was at last free from the wardship. However, John did not bother waiting for a dispensation from the Pope – which they needed as they were both great-grandchildren of King Henry – and this was the first of many disputes that John would have with the church. There have been some claims that the dispensation was later provided with the bizarre condition that they no longer have sexual relations with each other. Their childlessness was given as evidence of this, and it is portrayed as the reason for their divorce once John became King and needed an heir. However, it does seem odd that the Pope would impose this sanction on a married couple.
By 1193, the couple were estranged from each other, and it is presumed that Isabella retired to her own estates. The reason for the estrangement is not known. It is also likely that John entered into negotiations for another marriage and this implies that he did not consider himself married to Isabella. In May 1199, after the death of King Richard I, John returned to England to be crowned King. Isabella did not share his coronation, and there was apparently no suggestion that she would do so. His accession also prompted a renewed search for a bride, and without the dispensation, it was easy for John to annul his marriage to Isabella. However, she would not free from John. He took her into custody to prevent her from making a new marriage, and the Earldom of Gloucester was granted to someone else. Isabella resented the loss of her lands, but there was little she could do against the King. She spent her imprisonment in several places.
In 1214, her fortunes finally changed, though perhaps not for the better. John was in desperate need of funds, and he returned the Earldom of Gloucester to Isabella before selling her and her lands to Geoffrey de Mandeville, Earl of Essex, who paid 20,000 marks for the honour of marrying her. Though Isabella was being forced into this marriage, it also meant some form of freedom. However, the Earl of Essex missed the first instalment to the King and John responded by confiscating the Gloucester estates. The following rebellion and the signing of the Magna Carta led to the reinstatement of the estates. For the Earl of Essex, the joy was shortlived. He died on 23 February 1216 from wounds received in a tournament.
Isabella was, at last, independent. She issued several charters during this period with the words, “in my free widowhood.” King John died in 1216 and was succeeded by his 9-year-old son, now King Henry III. One of the young King’s regents, Hubert de Burgh, became Isabella’s third husband in 1217. She probably had no choice in the matter. Her third marriage was destined to be brief as Isabella died on 14 October 1217.
She was buried in Christ Church, Canterbury and the Earldom passed to her sister Amica.