Margaret of Anjou became queen of England through her marriage to Henry VI in 1445, a union intended to support peace with France. The agreement was followed by English withdrawal from Maine and the collapse of much of England's French position, developments opponents used against the court. Margaret's own authority depended on household resources, patronage, and alliances rather than a separate executive office. She also supported learning, issuing the foundation charter for Queens' College, Cambridge, in 1448.

Henry's prolonged incapacity in 1453 and the birth of their son Edward transformed her political position. She sought to protect the king and the prince's inheritance against Richard, duke of York, and his allies. As rival groups competed for control of government, Margaret became a central organizer of the Lancastrian cause. The conflict developed into the Wars of the Roses, in which changes of allegiance and regional power were as important as rival hereditary claims.

After the Yorkist victory at Northampton in 1460, an agreement recognized York as Henry's heir and displaced Edward. Margaret rejected that settlement and continued resistance. Lancastrian victories at Wakefield and the second battle of St Albans briefly strengthened her position, but defeat at Towton in 1461 drove her into exile. She sought military and financial assistance in Scotland and France while preserving her son's claim.

In 1470 she accepted an alliance with her former enemy, Richard Neville, earl of Warwick, against Edward IV. Henry VI was briefly restored, but the arrangement collapsed the next year. Warwick died at Barnet, and Margaret's forces were defeated at Tewkesbury, where her son was killed. Henry died in the Tower soon afterward. Margaret was imprisoned until Louis XI secured her release in 1475, and she spent her final years in France. Hostile portrayals of her ambition obscure a career shaped by civil war, an incapacitated husband, and her son's succession.