Jan Hus (c. 1369 – 6 July 1415), often referred to in English as John Hus or John Huss, is 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, as he lived before Luther, Calvin, and Zwingli.

He is burned at the stake for heresy against the doctrines of the Catholic Church, including those on ecclesiology, the Eucharist, and other theological topics.

Hus is a key predecessor to the Protestant movement of the sixteenth century, and his teachings have a strong influence on the states of Europe, most immediately in the approval of a reformist Bohemian religious denomination, and, more than a century later, on Martin Luther himself.

Between 1420 and 1431, the Hussite forces defeat five consecutive papal crusades against followers of Hus.

Their defense and rebellion against Roman Catholics become known as the Hussite Wars.

A century later, as many as 90% of inhabitants of the Czech lands are non-Catholic and follow the teachings of Hus and his successors.