Libertini, in ecclesiastical history, a religious sect, which arose in the year 1525, whose principal tenets were, that the Deity was the sole operating cause in the mind of man, and the immediate author of all human actions; that, consequently, the distinctions of good and evil, which had been established with regard to those actions, were false and groundless, and that men could not, properly speaking, commit sin; that religion consisted in the union of the spirit or rational soul with the Supreme Being; that all those who had attained this happy union, by sublime contemplation and elevation of mind, were then allowed to indulge, without exception or restraint, their appetites or passions; that all their actions and pursuits were then perfectly innocent; and that, after the death of the body, they were to be united to the Deity. They likewise said that Jesus Christ was nothing but a mere je ne sais quoi, composed of the spirit of God, and of the opinion of men.

These maxims occasioned their being called Libertines; The Libertini spread principally in Holland and Brabant. Their leaders were one Quintin, a Picard, Pocelius, Ruffus, and another called Chopin, who joined with Quintin, and became his disciple.

This sect obtained a certain footing in France through the favour and protection of Margaret, queen of Navarre, and sister to Francis I., and found patrons in several of the reformed churches. This sect was probably a remnant of the more ancient Beguards or Brethren of the Free Spirit.

Libertines of Geneva, were a cabal of rakes rather than of fanatics; for they made no pretences to any religious system, but pleaded only for the liberty of leading voluptuous and immoral lives. This cabal was composed of a certain number of licentious citizens, who could not bear the severe discipline of Calvin, who punished with rigour not only dissolute manners, but also whatever bore the aspect of irreligion and impiety. In this turbulent cabal there were several persons who were not only notorious for their dissolute and scandalous manner of living, but also for their atheistical impiety, and contempt of all religion. To this odious class belonged one Gruet, who denied the divinity of the Christian religion, the immortality of the soul, and difference between moral good and evil, and rejected with disdain the doctrines that are held most sacred among Christians; for which impieties he was at last brought before the civil tribunal, in the year 1550, and condemned to death. The Genevan spirit of reformation, improperly directed by the violence and zeal of Calvin, did at this time operate to a degree which has marked the character of this great reformer with reproach. For in 1544, Sebastian Castalio, master of the public school at Geneva, who was a man of probity, and distinguished by his learning and taste, was, nevertheless, deposed from his office and banished the city, because he disapproved some of the measures that were pursued and some of the opinions entertained by Calvin and his colleagues, and particularly that of absolute and unconditional predestination. Jerome Bolsec also, a man of genius and learning, who became a convert to the Protestant religion and fled to Geneva for protection, was cast into prison, and soon after sent into banishment, because, in 1551, he imprudently and indecently declaimed, in full congregation and at the close of public worship, against the doctrine of absolute decrees.