Johann Nikolaus von Hontheim (January 27, 1701 – September 2, 1790) was a German historian and theologian. He is remembered as Febronius, the pseudonym under which he wrote his 1763 treatise On the State of the Church and the Legitimate Power of the Roman Pontiff which offered Europe the "foremost formulation of the arguments against papal absolutism in Germany".
Born in Trier, he belonged to a noble family which had been for many generations connected with the court and government of the Electors of Trier, his father, Kaspar von Hontheim, being receiver-general of the Electorate. At the age of twelve, young Hontheim was given by his maternal uncle, canon of the collegiate church of St. Simeon (which at that time still occupied the Roman Porta Nigra at Trier), a prebend in his church, and on May 13, 1713 he received the tonsure. He was educated by the Jesuits at Trier and at the universities of Trier, Leuven and Leiden, taking his degree of doctor of laws at Trier in 1724. During the following years he traveled in various European countries, spending some time at the German College in Rome; in 1728 he was ordained priest and, formally admitted to the chapter of St Simeon in 1732, he became a professor at the University of Trier.
In 1738 he was sent on official duty to Coblenz by the Elector. In that capacity, he had plenty of opportunities to study the effect of the interference of the Roman Curia in the internal affairs of the Empire, notably in the negotiations that preceded the elections of the emperors Charles VII and Francis I in which Hontheim took part as assistant to the electoral ambassador. It appears that it was the extreme claims of the papal nuncio on these occasions and his interference in the affairs of the electoral college that first suggested to Hontheim that critical examination of the basis of the papal pretensions, the results of which he afterwards published to the world under the pseudonym of Febronius.
In 1747, broken down by overwork, he resigned his position as an official and retired to St. Simeon, of which he was elected dean in the following year. In May 1748, he was appointed by the archbishop-elector Francis George von Schönborn as his auxiliary bishop, being consecrated at Mainz, in February 1749, under the title of bishop of Myriophiri in partibus. Upon Hontheim as auxiliary bishop and vicar-general fell the whole spiritual administration of the diocese; this work, in addition to that of pro-chancellor of the university, he carried on single-handed until 1778, when Jean-Marie Cuchot d'Herbain was appointed his coadjutor. On April 21, 1779 he resigned the deanery of St Simeons on the ground of old age. He died on 2 September 1790 at his château at Montquintin near Orval, an estate which he had purchased. He was buried at first in St Simeons; but the church was ruined by the French during the revolutionary wars and never restored, and in 1803 the body of Hontheim was transferred to that of St Gervasius.