Charles IX of France was a king who ruled from 1560 to 1574. He was the son of Henry II and Catherine de' Medici. His reign was marked by the religious conflicts between Catholics and Protestants, known as the French Wars of Religion. One of the most significant events during his rule was the St. Bartholomew's Day Massacre in 1572, where thousands of Huguenots (French Protestants) were killed. Charles IX struggled with the pressures of his mother, Catherine, and the ongoing violence, which ultimately affected his mental health and led to his early death at the age of 23.