Jan Hus (commonly known as John Hus/Huss) is the chief Czech Reformer from the 14th century. He is considered to have been a major forerunner to Luther. A bit about Hus:

John Hus was born in 1369 in Husinec, Bohemia. When he was still quite young he moved to Prague, where he earned a living by singing and serving in churches. After attending the University of Prague and earning multiple degrees, Hus became an ordained priest in 1400 and within 2 years began preaching and teaching that the Catholic Church needed to be reformed. Hus was influenced in his theological views by John Wycliffe, and even translated some of Wycliffe's (illegal) works into Czech, so the people could read it.

Similar to Wycliffe, Hus preached against indulgences, the corruption of the clergy, and the failures of the pope. As Hus' teachings began to influence Bohemians, he and his followers (called Hussites) were excommunicated in 1410 by Alexander V. Hus continued to deliver public addresses, wherein he advocated such positions as no pope, bishop, or any other person has the right to take up the sword in the name of the Church, that prayer should be chosen over warfare. He also stated that forgiveness of sins can only be had by true repentance, not through money (buying indulgences or giving charitably). Being run out of Prague lest the city suffer attack on his behalf, he took to the rural areas around Prague, where he would publicly appeal to Christ as his authority; refusing to trust in kings and councils, popes and bishops, Hus saw Christ as the ultimate authority of faith.

Hus was summoned to the Council of Constance (which ran from 1414-1418), where he arrived on 3 November, 1414. Even though he was promised safe passage to and from the council, he was nonetheless imprisoned on the 28th of November. After months of trials and interrogations (lasting so long primarily because of his refusal to recant, stating he must be shown from Scripture where he was in error), he was finally condemned of heresy on the 6th of July, 1415. As he was tied to the stake where he was to be burnt alive, he was offered one last chance to recant of his views and actions. He refused, and so flame entwined with wood and flesh until nothing was left but ash.

Of his followers, the Hussites, they endured (and successfully repelled) 5 papal Crusades that were launched to eradicate their presence from Bohemia. Unfortunately for the Catholic Church, Hus’ influence had spread throughout the kingdom, and within a century nearly 90% of all citizens were Hussites. Unfortunately for the Hussites, their prominence in Czech lands would not last, as they would endure continued persecutions under the Catholic Habsburgs and would suffer a massive defeat which led to mass expulsion during the Thirty Years War at the Battle of White Mountain in 1620. Combine these persecutions at Catholic hands with severe persecution and restrictions under Communist rule in the 20th century, and what is now known as the Czech Republic is largely atheistic.

Sources: Wilhelm, Joseph. "Jan Hus." The Catholic Encyclopedia. Vol. 7. New York: Robert Appleton Company, 1910

Fudge, Thomas. "Jan Hus: Religious Reform and Social Revolution in Bohemia" 2010