Quietism is the name given (especially in Catholic theology) to a set of contemplative practices that rose in popularity in France, Italy, and Spain during the late 1670s and 1680s, particularly associated with the writings of the Spanish mystic Miguel de Molinos (and subsequently François Malaval and Madame Guyon), and which were condemned as heresy by Pope Innocent XI in the papal bull Coelestis Pastor of 1687. Quietism was seen by critics as holding that man's highest perfection consists in a sort of psychical self-annihilation and a consequent absorption of the soul into the Divine Essence even during the present life.

Since the late seventeenth century, Quietism has functioned (especially within Catholic theology, though also to an extent within Protestant theology), as the shorthand for accounts which are perceived to fall foul of the same theological errors, and thus to be heretical. As such, the term has come to be applied to beliefs far outside its original context. The term quietism was not used until the 17th century, so some writers have dubbed the expression of such errors before this era as "pre-quietism".

Ronald Knox, in his study of heterodox Christian movements, including Quietism, points out, however, that Quietism is less a heresy or school of thought than a "tendency," a "direction of the human mind" to exaggerate concepts that otherwise could be considered perfectly orthodox. He suggests that it is misleading to speak of a Quietist School, if by this we mean a well thought-out set of beliefs that all members of a supposed Quietist heresy professed. Quietism, he maintains, is not a neat set of "conclusions." Rather, he asserts, Quietism, as it manifested itself in seventeenth-century Europe, ran the spectrum from almost completely orthodox teaching to extremely heterodox beliefs. "You can, he concludes, "be more or less of a Quietist." One, therefore, should always bear in mind that many differences in style and emphasis (and in some cases even in rather essential beliefs) exist among the various mystics labeled Quietist. As Knox has shown, the teachings of Molinos are not necessarily synonymous with those of La Combe or Guyon, much less those of Fénelon.

Although both Molinos and other authors condemned in the late seventeenth century, as well as their opponents, spoke of the Quietists (in other words, those who were devoted to the "prayer of quiet", an expression used by Teresa of Avila, John of the Cross and others), "Quietism" was a creation of its opponents, a somewhat artificial systematisation made on the basis of ecclesiastical condemnations and commentary upon them. No single author – even Molinos, generally seen as the main representative of Quietist thought – advocated all the positions that formed the Quietism of later Catholic doctrinal textbooks; as such, at least one author suggests that it is better to speak of a Quietist tendency or orientation, one which may be located in analogous forms through Christian history.

Quietism is particularly associated with the writings of Miguel de Molinos. He published the Spiritual Guide in 1675. Molinos recommended absolute passivity and contemplation in total repose of the spirit. He was aware of the focus in the writings of Ignatius of Loyola on meditation, and the likelihood that Jesuit writers would react poorly to any perceived attack on Ignatius’s thought. He said the meditation was an important stage of the spiritual life, but that it was well-established that in order to pass to the state of contemplation one must leave behind meditative practices.

The doctrines of quietism were finally condemned by Pope Innocent XI in the papal bull of 1687 entitled Coelestis Pastor. However, theologian Bernard McGinn says that the particular errors condemned in the bull are not in the Spiritual Guide. Molinos' work was marked by imprecision and ambiguities that left it subject to unintended interpretations.

From Molinos' teaching developed a less radical form known as Semiquietism, whose principle advocates were François Fénelon and Madame Guyon. Quietism spread among Catholics through small groups into France. The most noted representative was Madame Guyon, especially with her work A Short and Easy Method of Prayer, who claimed not to have known the teaching of Molinos directly, but certainly did have contact with François Malaval, a proponent of Molinos.

Madame Guyon won an influential convert at the court of Louis XIV in Madame de Maintenon, and influenced the circle of devout Catholics in the court for a time. She was also a spiritual counsellor to François Fénelon, Archbishop of Cambrai. A commission in France found most of Madame Guyon's works intolerable and the government confined her, first in a convent, then in the Bastille, leading eventually to her exile to Blois in 1703.