Isabella, daughter of the French king, Philip the Fair, had been destined as the bride of Edward of Carnarvon, the future Edward II of England from the tender age of four . They were formally betrothed When Isabella was eight and in 1308 Edward, the new King of England, sailed to Boulogne to marry his bride. She was twelve and he twenty-three. Isabella's reputed charm was said to have lost Edward Scotland as he hastened to leave the country with affairs unsettled to marry her as soon as possible. If the story is true, it was one of the few occasions on which Edward showed any desire to please Isabella. Throughout her marriage Isabella had to share Edward with his favourites. First Piers Gaveston engaged Edward's affections. To him Edward gave the jewels and rings which had been his wedding present. Isabella felt the slight keenly. When the English barons grew as tired as Isabella of this royal favourite, Thomas, the Earl of Lancaster, as leader of the opposition, wrote to the Queen declaring he would not rest until he had rid her of the presence of Gaveston. After a short exile, however, Gaveston returned. Edward ignored his queen's complaints that Gaveston insulted her and caused her to write to her father that she was the most wretched of queens.

Relations between husband and wife improved after Gaveston's murder in 1312. Their first child was born in November 1312 and Edward was delighted at the birth of an heir, the future Edward III. Three more children were horn to them, John of Eltham in 1316, Eleanor of Woodstock in 1318, and Joan of the Tower in 1321. Isabella was given a household, with a staff of at least one hundred and eighty, and generous estates, including the important honors of Wallingford and St. Valery. Further, the death of her mother-in-law in 1318 released many important manors to Isabella. It was probably the happiest period of their marriage.
Isabella finally turned against her husband , due to the rise of the Despenser family in the 1320s . She wrote to her brother Charles that "she was held in no higher consideration than a servant in the palace of the King her husband". There were even rumours , that the younger Despenser was trying to engineer the annulment of Edward and Isabella's marriage. The first open move against her was the confiscation of her estates in 1324 on the flimsy pretext of the danger of a French invasion. Isabella's position was intolerable.
Isabella was quick to seize an escape route. In 1325 Edward unthinkingly sent her on a diplomatic mission to France. Her negotiations were successful and it was agreed that Edward's French possessions should be returned to him. The young Edward III therefore sailed for France to do homage for these lands. With the heir to the throne at her side Isabella played her trump card. She declared that neither she nor her son would return to court until the younger Despenser had been removed. At the same time she told her brother that her marriage had been broken and that she must live a widow until the Despensers had been removed from power . She found comfort in the arms of Roger Mortimer, an English baron with a French wife. Isabella had first met Mortimer when he was a prisoner in the Tower of London. In Paris they met again. The affair was so open that soon their liaison began to cause scandal. The pair withdrew to the Low Countries and there prepared to invade England.
When they landed in 1326 many people flocked to their side , when pressing westward in pursuit of her husband Isabella posted a proclamation in London asking particularly for the destruction of the Despensers. At Bristol and at Neath the Despensers were hunted down, tried, and killed. Edward himself was imprisoned at Kenilworth while Isabella and Mortimer rallied support in London for his deposition. In January 1327 he handed over his crown revenge was complete. Edward was still alive and a danger , in September 1327 he was horribly murdered at Berkeley Castle, doubtless at Mortimer's instigation.
For three years Isabella and Mortimer ruled between them in the name of the young Edward III. Isabella's endowment was restored to her, with a generous increase. In 1330 Mortimer fell from power and Isabella escaped comparatively unscathed returning her gains an given an allowance of £3,000 a year she was allowed to move freely around the country. At her favourite Castle at Rising she maintained a degree of state, amusing herself by hawking, reading, or hearing romances, and collecting relics. In her old age she took the habit of the Poor Clares ,an unlikely candidate for the convent, and was buried in the Franciscan church at Newgate.