Unitas Fratrum, (Latin: “Unity of Brethren”), Protestant religious group inspired by Hussite spiritual ideals in Bohemia in the mid-15th century. They followed a simple, humble life of nonviolence, using the Bible as their sole rule of faith. They denied transubstantiation but received the Eucharist and deemed religious hymns of great importance. In 1501 they printed the first Protestant hymnbook, and in 1579–93 they published a Czech translation of the Bible (the Kralice, or Kralitz, Bible), the outstanding quality of which made it a landmark in Czech literature. Their Confessio Bohemica, reflecting Lutheran and Calvinist influences, effected a union with Lutheran Hussites in 1575 that received Holy Roman imperial sanction in 1609. By that time the Unitas Fratrum constituted half of the Protestants in Bohemia and more than that in Moravia. About the mid-16th century, Unitas emigrants moved into Poland and survived there for some two centuries.
Having joined the Czech estates in their fight with the Holy Roman emperor Ferdinand I (Thirty Years’ War), the Unitas Fratrum forces’ defeat in 1620 at the Battle of the White Mountain was a prelude to their suppression. In 1627 an imperial edict outlawed all Protestants in Bohemia. The Unitas was destroyed, with all its churches, its Bible, and its hymnbooks, and its members were forcibly “catholicized” or exiled. Remnants of the group, however, eventually found refuge in Saxony and under the name of Herrnhuters had great religious influence through their missionary activities. Both the Moravian Church and the Evangelical Czech Brethren Church in the Czech Republic trace their origin to the Unitas Fratrum.