Jan Hus was a Czech theologian and reformer who lived in the late 14th and early 15th centuries. He is best known for his criticism of the Catholic Church and its practices, advocating for reforms that emphasized the importance of the Bible and preaching in the vernacular. His ideas were influenced by the earlier work of John Wycliffe, an English reformer. Hus's teachings gained significant support, leading to his excommunication and eventual arrest. He was tried for heresy and burned at the stake in 1415. His martyrdom sparked the Hussite Wars, a series of conflicts in Bohemia that sought to implement his reforms and challenge the authority of the Church.