Jan Hus (; c. 1369 – 6 July 1415), often referred to in English as John Hus or John Huss, was a Czech priest, philosopher, reformer, and master at Charles University in Prague. After John Wycliffe, the theorist of ecclesiastical Reformation, Hus is considered the first Church reformer (living prior to Luther, Calvin, and Zwingli).
He is famed for having been burned at the stake for heresy against the doctrines of the Catholic Church, including those on ecclesiology, the Eucharist, and other theological topics. Hus was a key predecessor to the Protestant movement of the sixteenth century, and his teachings had a strong influence on the states of Europe, most immediately in the approval for the existence of a reformist Bohemian religious denomination, and, more than a century later, on Martin Luther himself.
Between 1420 and 1431, the Hussite forces defeated five consecutive papal crusades against followers of Hus. Their defence and rebellion against Roman Catholics became known as the Hussite Wars. A century later, as many as 90% of inhabitants of the Czech lands were non-Catholic and followed the teachings of Hus and his successors.