Henry III of Castile was a king who ruled from 1390 to 1406. He was born on October 4, 1379, and was the son of John I of Castile and Leonor of Aragon. His reign is noted for efforts to strengthen the monarchy and improve relations with the nobility. Henry III faced challenges, including conflicts with the Kingdom of Aragon and internal strife among the nobility. He is also remembered for his support of the Catholic Church and for promoting cultural developments in Castile. He died on December 25, 1406, and was succeeded by his son, John II of Castile.