Margaret was born at Bletsoe Castle, Bedfordshire, on 31 May 1443 or 1441. The day and month are not disputed, as she required Westminster Abbey to celebrate her birthday on 31 May. The year of her birth is more uncertain. William Dugdale, the 17th century antiquary, has suggested that she may have been born in 1441; this suggestion is based on evidence of inquisitions taken at the death of Margaret’s father. Dugdale has been followed by a number of Margaret’s biographers; however, it is more likely that she was born in 1443, as in May 1443, her father had negotiated with the King about the wardship of his unborn child in case he died on a campaign.  She was the daughter of Margaret Beauchamp of Bletsoe and John Beaufort, 1st Duke of Somerset. Margaret’s father was a great-grandson of King Edward III through his third surviving son, John of Gaunt, Duke of Lancaster. At the moment of her birth, Margaret’s father was preparing to go to France and lead an important military expedition for King Henry VI. Somerset negotiated with the king to ensure that, in case of his death, the rights to Margaret’s wardship and marriage would belong only to his wife.  Somerset fell out with the king after coming back from France, however, and he was banished from the court and about to be charged with treason. He died shortly afterwards. According to Thomas Basin, Somerset died of illness, but the Crowland Chronicle reported that his death was suicide. Margaret, as his only child, was the heiress to his fortunes.  On Margaret’s first birthday, the King broke the arrangement with Margaret’s father and gave her wardship to William de la Pole, 1st Duke of Suffolk, although Margaret remained with her mother. Margaret’s mother was pregnant at the time of Somerset’s death but the child did not survive and Margaret remained sole heir. Although she was her father’s only legitimate child, Margaret had two half-brothers and three half-sisters from her mother’s first marriage, whom she supported after her son’s accession.

Margaret was married to Suffolk’s son, John de la Pole. The wedding may have been held between 28 January and 7 February 1444, when she was perhaps a year old but certainly no more than three. However there is more evidence to suggest they were married in January 1450, after Suffolk was arrested and looking to secure his son’s future. Papal dispensation was granted on 18 August 1450 because the spouses were too closely related and this concurs with the later date of marriage.  Three years later, the marriage was dissolved and King Henry VI granted Margaret’s wardship to his own half-brothers, Jasper and Edmund Tudor. Margaret never recognised this marriage. In her will, made in 1472, Margaret refers to Edmund Tudor as her first husband. Under canon law, Margaret was not bound by the marriage contract as she was entered into the marriage before reaching the age of twelve.

Even before the annulment of her first marriage, Henry VI chose Margaret as a bride for his half-brother, Edmund Tudor, 1st Earl of Richmond. Edmund was the eldest son of the King’s mother, Catherine of Valois, by Owen Tudor.  Margaret was 12 when she married the 24-year-old Edmund Tudor on 1 November 1455. The Wars of the Roses had just broken out; Edmund, a Lancastrian, was taken prisoner by Yorkist forces less than a year later. He died of the plague in captivity at Carmarthen the following November, leaving a 13-year-old widow who was seven months pregnant with their child.

Taken into the care of her brother-in-law Jasper, at Pembroke Castle, the Countess gave birth on 28 January 1457 to her only child, Henry Tudor, the future Henry VII of England. The birth was particularly difficult; at one point, both the Countess and her child were close to death, due to her young age and small size. After this difficult birth she would never give birth again.  Margaret and her son remained in Pembroke until the York triumphs of 1461 saw the castle pass to Lord Herbert of Raglan. From the age of two Henry lived with his father’s family in Wales, and from the age of fourteen he lived in exile in France. During this period, the relationship between mother and son was sustained by letters and a few visits.  The Countess always respected the name and memory of Edmund as the father of her only child. In 1472, sixteen years after his death, Margaret specified in her will that she wanted to be buried alongside Edmund, even though she had enjoyed a long, stable and close relationship with her third husband, who had died in 1471.

Even before the annulment of her first marriage, Henry VI chose Margaret as a bride for his half-brother, Edmund Tudor, 1st Earl of Richmond. Edmund was the eldest son of the King’s mother, Catherine of Valois, by Owen Tudor.  Margaret was 12 when she married the 24-year-old Edmund Tudor on 1 November 1455. The Wars of the Roses had just broken out; Edmund, a Lancastrian, was taken prisoner by Yorkist forces less than a year later. He died of the plague in captivity at Carmarthen the following November, leaving a 13-year-old widow who was seven months pregnant with their child.

Taken into the care of her brother-in-law Jasper, at Pembroke Castle, the Countess gave birth on 28 January 1457 to her only child, Henry Tudor, the future Henry VII of England. The birth was particularly difficult; at one point, both the Countess and her child were close to death, due to her young age and small size. After this difficult birth she would never give birth again.  Margaret and her son remained in Pembroke until the York triumphs of 1461 saw the castle pass to Lord Herbert of Raglan. From the age of two Henry lived with his father’s family in Wales, and from the age of fourteen he lived in exile in France. During this period, the relationship between mother and son was sustained by letters and a few visits.  The Countess always respected the name and memory of Edmund as the father of her only child. In 1472, sixteen years after his death, Margaret specified in her will that she wanted to be buried alongside Edmund, even though she had enjoyed a long, stable and close relationship with her third husband, who had died in 1471.

In June 1472, Margaret married Thomas Stanley, the Lord High Constable and King of Mann. Their marriage was at first a marriage of convenience. Recent historians have suggested that Margaret never considered herself a member of the Stanley family.Margaret’s marriage to Stanley enabled her to return to the court of Edward IV and Elizabeth Woodville. She was chosen by Queen Elizabeth to be godmother to one of her daughters.  Following Edward’s death and the seizure of the throne by Richard, Margaret was soon back at court serving the new queen, Anne Neville. Margaret carried Anne’s train at the coronation. Nevertheless, Richard III passed an act of Parliament stripping Margaret of all her titles and estates, although he stopped short of a full attainder by transferring her property to her husband.  However, whilst serving the new king and queen, Margaret was secretly plotting with the dowager queen, Elizabeth Woodville, and was almost certainly involved in Buckingham’s rebellion. As Queen Elizabeth’s sons, the Princes in the Tower, were presumed murdered, it was agreed that Margaret’s son, Henry, would be betrothed to Elizabeth of York, the eldest daughter of Elizabeth and Edward IV, thus creating a marriage alliance with potential to attract both Yorkist and Lancastrian support.

Margaret’s husband Stanley, despite having fought for Richard III during the Buckingham rebellion, did not respond when summoned to fight at the Battle of Bosworth Field in 1485, remaining aloof from the battle, even though his eldest son, George Stanley (styled Lord Strange), was held hostage by Richard. After the battle, it was Stanley who placed the crown on the head of his stepson (Henry VII), who later made him Earl of Derby. Margaret was then styled “Countess of Richmond and Derby”.  Later in her marriage, the Countess preferred living alone. In 1499, with her husband’s permission, she took a vow of chastity in the presence of Richard FitzJames, Bishop of London. Taking a vow of chastity while being married was unusual but not unprecedented; around 1413, Margery Kempe also negotiated a vow of chastity with her husband. The Countess moved away from her husband and lived alone at Collyweston. She was regularly visited by her husband, who had rooms reserved for him. Margaret renewed her vows in 1504.

After her son won the crown at the Battle of Bosworth Field, the Countess was referred to in court as “My Lady the King’s Mother”. As such, she enjoyed legal and social independence which other married women could not (see Coverture). Her son’s first parliament recognised her right to hold property independently from her husband, as if she were unmarried. Towards the end of her son’s reign she was given a special commission to administer justice in the north of England.  As arranged by their mothers, Henry married Elizabeth of York. The Countess was reluctant to accept a lower status than the dowager queen Elizabeth or even her daughter-in-law, the queen consort. She wore robes of the same quality as the queen consort and walked only half a pace behind her. Elizabeth’s biographer, Amy Licence, states that this “would have been the correct courtly protocol”, adding that “Only one person knew how Elizabeth really felt about Margaret and she did not commit it to paper.” Despite this, Margaret could not do anything that Elizabeth forbade; as Queen, Elizabeth – by all legal rights and through marriage – outranked Margaret as a Queen to a Countess.

Margaret had written her signature as M. Richmond for years, since the 1460s. In 1499, she changed her signature to Margaret R., perhaps to signify her royal authority (R standing either for regina – queen in Latin as customarily employed by female monarchs – or for Richmond). Furthermore, she included the Tudor crown and the caption et mater Henrici septimi regis Angliæ et Hiberniæ (“and mother of Henry VII, king of England and Ireland”).  Many historians believe the departure from court of dowager queen Elizabeth Woodville in 1487 was partly at the behest of Henry’s influential mother, though this is uncertain. The Countess was known for her education and her piety, and her son is said to have been devoted to her. He died on 21 April 1509, having designated his mother chief executor of his will. She arranged her son’s funeral and her grandson’s coronation. At her son’s funeral she was given precedence over all the other women of the royal family.

The Countess died in the Deanery of Westminster Abbey on 29 June 1509. This was the day after her grandson’s 18th birthday, and just over two months after the death of her son. She is buried in the Henry VII Lady Chapel of the Abbey, in a black marble tomb topped with a bronze gilded effigy and canopy. She is now situated between the later graves of William and Mary and the tomb of Mary, Queen of Scots.