structural:scholar_edition, quality:correction
Louis IX (25 April 1214 – 25 August 1270), also known as Saint Louis, was King of France from 1226 until his death in 1270. He is widely recognized as the most distinguished of the Direct Capetians. Following the death of his father, Louis VIII, he was crowned in Reims at the age of 12. His mother, Blanche of Castile, effectively ruled the kingdom as regent until he came of age and continued to serve as his trusted adviser until her death. During his formative years, Blanche successfully confronted rebellious vassals and championed the Capetian cause in the Albigensian Crusade, which had been ongoing for the past two decades.

As an adult, Louis IX grappled with persistent conflicts involving some of the most influential nobles in his kingdom, including Hugh X of Lusignan and Peter of Dreux. Concurrently, England's Henry III sought to reclaim the Angevin continental holdings, only to be decisively defeated at the Battle of Taillebourg. Louis expanded his territory by annexing several provinces, including parts of Aquitaine, Maine, and Provence. Keeping a promise he made while praying for recovery from a grave illness, Louis led the ill-fated Seventh and Eighth Crusades against the Muslim dynasties that controlled North Africa, Egypt, and the Holy Land. He was captured and ransomed during the Seventh Crusade, and later succumbed to dysentery during the Eighth Crusade. His son, Philip III, succeeded him.

Louis instigated significant reforms in the French legal system, creating a royal justice mechanism that allowed petitioners to appeal judgements directly to the monarch. He abolished trials by ordeal, endeavored to terminate private wars, and incorporated the presumption of innocence into criminal proceedings. To implement his new legal framework, he established the offices of provosts and bailiffs. Louis IX's reign is often marked as an economic and political zenith for medieval France, and he held immense respect throughout Christendom. His reputation as a fair and judicious ruler led to his being solicited to mediate disputes beyond his own kingdom.

Louis' admirers through the centuries have celebrated him as the quintessential Christian monarch. His skill as a knight and engaging manner with the public contributed to his popularity, although he was occasionally criticized as being overly pious, earning the moniker of a " monk king". Louis was a staunch Christian and rigorously enforced Catholic orthodoxy. He enacted harsh laws against blasphemy, and he also launched actions against France's Jewish population, including ordering them to wear a yellow badge of shame, as well as the notorious burning of the Talmud following the Disputation of Paris. Louis IX holds the distinction of being the sole canonized king of France.