Johann Arndt (or Arnd; 27 December 1555 – 11 May 1621) was a German Lutheran theologian and mystic who wrote several influential books of devotional Christianity.

He continued his studies in Strasbourg, under the professor of Hebrew, Johannes Pappus (1549–1610), a zealous Lutheran, the crown of whose life's work was the forcible suppression of Calvinistic preaching and worship in the day, and who had great influence over him.

[1] In Basel, again, he studied theology under Simon Sulzer (1508–1585), a broad-minded divine of Lutheran sympathies, whose aim was to reconcile the churches of the Helvetic and Wittenberg confessions.

These were mainly of a mystical and devotional kind, and were inspired by St Bernard, Johannes Tauler and Thomas à Kempis.

Both these books have been translated into English: Paradiesgärtlein with the title the Garden of Paradise, and Wahres Christentum as True Christianity.

[4] In 2022, Johann Ardt was officially added to the Episcopal Church liturgical calendar along with Jacob Boehme with a feast day on 11 May.