The Countess of Richmond & Derby, commonly called Lady Margaret Beaufort, was the daughter of John Beaufort, Duke of Somerset (son of John of Gaunt by Catherine Swynford), and his wife, Margaret Beauchamp. At the age of about seven, she became the child bride of John De La Pole, 2nd Duke of Suffolk, but the union was later dissolved. The Beaufort stock, though originally bastard, was legitimized by an Act of Parliament in Richard II’s reign. Thus, on the failure of the heirs of King Henry VI, Margaret's claim to the crown of England became quite a possible one (1471). Such as it was, however, the Lancastrian title had originally rested, if on anything beyond usurpation or parliamentary election, on the exclusion of females.

Henry VI always looked upon the Beauforts as possible heirs and, in 1455, married the twelve-year-old Margaret to his own maternal half-brother, Edmund Tudor, Earl of Richmond (then aged twenty-five). Her son, afterwards Henry VII, was born in 1456, and her husband died in the same year. She, soon afterward, married Henry Stafford, the second son of the Duke of Buckingham, and submitted to the Yorkist rule; but, after the Battle of Tewkesbury, she was obliged to send her son, Henry, now the sole hope of the Lancastrian cause, to seek refuge in Brittany.

Margaret's third husband was a pronounced Yorkist, Thomas, Lord Stanley, afterwards Earl of Derby; but his final defection from Richard III on the field of Bosworth secured the victory to his stepson, Henry VII. Margaret, though she seldom appeared at her son's court, remained, until her death, his constant correspondent and one of his wisest advisers. She took vows of religion in 1504, but continued to live out of a nunnery, although she had founded several.

Her great glory is, however, her foundation of the two Colleges of Christ's and St. John's at Cambridge, and of the' Lady Margaret' professorships of Divinity at both Universities. She was instigated to these foundations by the advice of John Fisher, afterwards Bishop of Rochester, one of the glories, as indeed Margaret herself also was, of Renaissance learning in England. Margaret was an ardent patron of the Early English Press and her grandson Henry VIII's love of learning and books was no doubt a direct inheritance from her.