Joan was the daughter of Edmund of Woodstock, 1st Earl of Kent, and Margaret Wake, 3rd Baroness Wake of Liddell. Her father Edmund was the son of King Edward I and his second wife, Margaret of France, daughter of Philip III of France. Edmund’s support of his older half-brother, King Edward II of England, placed him in conflict with the queen, Isabella of France, and her lover Roger Mortimer, 1st Earl of March. Edmund was executed after Edward II’s deposition, and Joan’s mother, along with her children, was placed under house arrest in Arundel Castle when Joan was only two years old.  The Earl’s widow, Margaret, was left with four children for whom to care. Joan’s first cousin, the new King Edward III, took on the responsibility for the family, and looked after them well. His wife, Queen Philippa, was Joan’s second cousin.  In 1340, at the age of twelve, Joan secretly married Thomas Holland of Upholland, Lancashire, without first gaining the royal consent necessary for couples of their rank. The following winter (1340 or 1341), while Holland was overseas, her family forced her to marry William Montacute, son and heir of the first Earl of Salisbury. Joan later averred that she did not disclose her existing marriage with Thomas Holland because she had been afraid that disclosing it would lead to Thomas’s execution for treason upon his return. She may also have become convinced that the earlier marriage was invalid.  Several years later, Thomas Holland returned from the Crusades, having made his fortune and the full story of his relationship with Joan came out. He appealed to the Pope for the return of his wife and confessed the secret marriage to the king. When the Earl of Salisbury discovered that Joan supported Holland’s case, he kept her a prisoner in her own home. In 1349, Pope Clement VI annulled Joan’s marriage to the Earl and sent her back to Thomas Holland, with whom she lived for the next eleven years. They had five children before Holland died in 1360.

Evidence of the affection of Edward, the Black Prince (who was her first cousin once removed) for Joan may be found in the record of his presenting her with a silver cup, part of the booty from one of his early military campaigns. Edward’s parents did not, however, favour a marriage between their son and their former ward. Queen Philippa had made a favourite of Joan at first, but both she and the king seem to have been concerned about Joan’s reputation. English law was such that Joan’s living ex-husband, Salisbury, might have claimed any children of her subsequent marriages as his own. In addition, Edward and Joan were within the prohibited degrees of consanguinity. The secret marriage they allegedly contracted in 1360 would have been invalid because of the consanguinity prohibition. At the King’s request, the Pope granted a dispensation allowing the two to be legally married. The official ceremony occurred on 10 October 1361, at Windsor Castle with the King and Queen in attendance. The Archbishop of Canterbury presided. In 1362, the Black Prince was invested as Prince of Aquitaine, a region of France which belonged to the English Crown since the marriage of Eleanor of Aquitaine and Henry II. He and Joan moved to Bordeaux, the capital of the principality, where they spent the next nine years. Two sons were born in France to the royal couple. The elder son, named Edward (27 January 1365 – 1370) after his father and grandfather, died at the age of six. Around the time of the birth of their younger son, Richard, the Prince was lured into a war on behalf of King Peter of Castile. The ensuing battle was one of the Black Prince’s greatest victories, but King Peter (Spanish: Pedro) was later killed, and there was no money to pay the troops. In the meantime, the Princess was forced to raise another army, because the Prince’s enemies were threatening Aquitaine in his absence.

By 1371, the Black Prince was no longer able to perform his duties as Prince of Aquitaine, and returned to England, where plague was wreaking havoc. In 1372, he forced himself to attempt one final, abortive campaign in the hope of saving his father’s French possessions. His health was now completely shattered. On 7 June 1376, a week before his forty-sixth birthday, he died in his bed at Westminster.  Joan’s son was next in line to succeed King Edward III. Edward III died on 21 June 1377 and Richard became King. He was crowned Richard II at the age of 10 in the following month. Early in his reign, the young King faced the challenge of the Peasants’ Revolt. The Lollards, religious reformers led by John Wyclif, had enjoyed the protection of Joan of Kent, but the violent climax of the popular movement for reform reduced the feisty Joan to a state of terror, while leaving the King with an improved reputation. As a power behind the throne, she was well loved for her influence over the young king – for example, on her return to London (via her Wickhambreaux estate) from a pilgrimage to Becket’s shrine at Canterbury Cathedral in 1381, she found her way barred by Wat Tyler and his mob of rebels on Blackheath but was not only let through unharmed, but saluted with kisses and provided with an escort for the rest of her journey.

In 1385, Sir John Holland, an adult son of her first marriage, was campaigning with the King in the Kingdom of Scotland, when a quarrel broke out between him and Ralph Stafford, son of the 2nd Earl of Stafford, a favourite of the new Queen Anne of Bohemia. Stafford was killed, and John Holland sought sanctuary at the shrine of St John of Beverley. On the King’s return, Holland was condemned to death. Joan pleaded with her son for four days to spare his half-brother. On the fifth day (the exact date in August is not known), she died, at Wallingford Castle. Richard relented, and pardoned Holland (though he was then sent on a pilgrimage to the Holy Land). Joan was buried, as requested in her will, at the Greyfriars, the site of the present hospital, in Stamford in Lincolnshire, beside her first husband. Her third husband, the Black Prince, had built a chantry for her in the crypt of Canterbury Cathedral (where he was to have been buried), with ceiling bosses of her face. Another boss in the north nave aisle is also said to be of her.