The French king who provided aid to Margaret of Anjou during the Wars of the Roses was Louis XI. His support was driven less by personal loyalty than by French strategy: a divided England was less likely to threaten France or form a dangerous alliance with Burgundy.
After Edward IV defeated the Lancastrians in 1461, Margaret fled with Edward of Westminster and sought help abroad. Louis received her cause sympathetically and supported Lancastrian efforts with money, military assistance and diplomacy. In 1462, he helped Margaret prepare an expedition against Edward IV, though the campaign failed to recover the English throne.
Louis’s most important contribution came later. When Richard Neville, Earl of Warwick, quarrelled with Edward IV, Louis helped broker an alliance between Warwick and Margaret—former enemies who agreed to restore Henry VI. Their plan briefly succeeded in 1470, creating the Readeption. Louis also later paid for Margaret’s release after her capture, under the Treaty of Picquigny in 1475. Charles VII was Margaret’s uncle and had arranged her marriage, but Louis XI was the king who aided her Lancastrian cause during the civil wars.