Johann Arndt was a German Lutheran theologian who wrote several influential books of devotional Christianity. Although reflective of the period of Lutheran Orthodoxy, he is seen as a forerunner of Pietism, a movement within Lutheranism that gained strength in the late 17th century.

Lutheranism is a major branch of Protestantism, identifying primarily with the theology of Martin Luther, the 16th-century German monk and reformer whose efforts to reform the theology and practices of the Catholic Church launched the Protestant Reformation.