Joseph (or Josef) Wilhelm Karl Kleutgen (9 April 1811 – 13 January 1883) was a German Jesuit theologian and philosopher. High official in the government of the Society of Jesus, he was also an expert at the Vatican I council.
Kleutgen was born in Dortmund, Westphalia. He began his studies with the intention of becoming a priest, but owing to the Protestant atmosphere of the school which he attended, his zeal for religion gradually cooled. From 28 April 1830, to 8 January 1831, he studied philology at the University of Munich. He was intensely interested in Plato's philosophy and the Greek tragic poets. Though he clung to the Catholic faith, it ceased to be the ruling principle of his life, and he fell into a deep melancholy.
In this state he was about to enter upon a secular career, when he suddenly received what he always regarded as a special illumination from heaven. Still he was not at rest. During the preceding years he had imbibed certain ideas from Lessing's and Herder's writings, which he could not reconcile with the Christian faith. After several weeks of internal conflict he betook himself to prayer, and to his astonishment many of his difficulties vanished at once; the remainder disappeared gradually. At Easter 1832 he entered the theological academy of Münster, and after two terms went to the seminary at Paderborn, where he was ordained subdeacon on 22 February 1834. On 28 April he entered the Society of Jesus at Brig, Switzerland, and, to avold any trouble with the German Government in the matter of military service, he became a naturalized citizen in one of the Swiss cantons, and changed his name to "Peters". After his ordination to the priesthood in 1837 he was professor of ethics in Fribourg, Switzerland, for two years; he then taught rhetoric in Brig from 1840 till 1843. In 1843 he was appointed professor of sacred eloquence in the German College, Rome.