Louis IX of France was a medieval monarch who ruled his kingdom from 1226 until his death in 1270. Born in Poissy, he ascended to the throne at age twelve under the regency of his mother, Blanche of Castile. He is recognized as the only French king to be canonized as a saint. His reign is noted for significant legal reforms and territorial expansion, though it ended during the Eighth Crusade in Tunis, where he died from dysentery.