Charles IX (27 June 1550 – 30 May 1574) was King of France from 1560 until his death in 1574 from tuberculosis. He ascended the throne of France upon the death of his brother Francis II in 1560. Charles was the twelfth king from the House of Valois, the fifth from the Valois-Orléans branch, and the fourth from the Valois-Orléans-Angoulême branch.
After decades of tension, war broke out between Protestants and Catholics after the massacre of Vassy in 1562. In 1572, after several unsuccessful peace attempts, Charles ordered the marriage of his sister Margaret of Valois to Henry of Navarre (the future King Henry IV of France), a major Protestant nobleman who was in the line of succession to the French throne, in a last desperate bid to reconcile his people. Facing popular hostility against this policy of appeasement, Charles allowed the massacre of all Huguenot leaders who gathered in Paris for the royal wedding at the instigation of his mother Catherine de' Medici. This event, known as the St. Bartholomew's Day massacre, was a significant blow to the Huguenot movement, though religious civil warfare soon began anew. Charles sought to take advantage of the disarray of the Huguenots by ordering the Siege of La Rochelle, but was unable to take the Protestant stronghold.
Much of his decision making was influenced by his mother Catherine de' Medici, a fervent Roman Catholic who initially sought peace between Catholics and Protestants, but after the St. Bartholomew's Day Massacre supported the persecution of Huguenots.
Charles died of tuberculosis without legitimate male issue in 1574 and was succeeded by his brother Henry III.