Charles IX became king of France in 1560 as a child, leaving his mother, Catherine de' Medici, to direct the regency. His reign unfolded amid struggles among the crown, powerful noble families, and Catholic and Protestant factions. The massacre at Vassy in 1562 helped trigger the first of the French Wars of Religion, forcing royal government to alternate military action with negotiated concessions.

The Peace of Amboise in 1563 permitted restricted Protestant worship. Charles and Catherine then undertook a lengthy royal tour intended to display authority and strengthen allegiance across the kingdom. The Edict of Roussillon standardized the beginning of the year on January 1. Renewed conflict in 1567 and 1568 exposed the weakness of attempts to maintain religious peace, while royal victories at Jarnac and Moncontour in 1569 failed to eliminate the Huguenot cause.

The Peace of Saint-Germain in 1570 again granted Protestants limited protections. Admiral Gaspard de Coligny acquired influence with Charles and encouraged intervention against Spain in the Netherlands, a policy resisted by others at court. The marriage of the king's sister Margaret to the Protestant Henry of Navarre in August 1572 brought leading Huguenots to Paris and appeared to offer an opportunity for reconciliation.

An attempt to kill Coligny was followed by the royal decision to eliminate Protestant leaders. Charles authorized the killings that began on August 24, but violence expanded far beyond the initial targets into the St. Bartholomew's Day massacres in Paris and provincial towns. Responsibility for planning, the king's intentions, and casualty totals remain debated; his authorization nevertheless implicated the monarchy directly. Further warfare followed, including the siege of La Rochelle. Charles died at Vincennes in 1574 and was succeeded by his brother Henry III. His efforts to exercise royal authority repeatedly foundered on confessional conflict and the crown's own resort to violence.