Pietism, originally, a German Lutheran reform movement of the 17th and 18th centuries which emphasized individual conversion, “living faith”, and the fruits of faith in daily life. The name Pietism is derived from the collegia pietatis (informal devotional meetings) organized by Philipp Jakob Spener while he was a pastor in Frankfurt. First held in Spener's home on Sunday afternoons, these meetings soon became popular across Germany. Participants did not separate from the established Church and its worship but tried to change the Church from within. They held prayer meetings, studied the Bible individually and in small groups, and led a disciplined Christian life. Claiming that faith is not the acceptance of correct theological propositions but trust in Christ, they insisted that pastors should have such faith in addition to their theological learning. Convinced that the world could be won for Christ through the conversion and Christian training of individuals, Pietists stressed the importance of education.

August Hermann Francke, whom Spener recruited, was a brilliant organizer and teacher who made the newly founded University of Halle the intellectual centre of Pietism. The university and other institutions organized by Francke in Halle sent out lay and clerical leaders to influence the ruling class of Protestant Germany and the younger generation of pastors. They also prepared missionaries for service around the world. Many of the Lutheran pastors in colonial America were Pietists educated at Halle, and so were most of the early Protestant missionaries in Africa and Asia.

Pietism was influenced by English Puritanism through German translations of the works of Richard Baxter, Lewis Bayly, and John Bunyan, and in turn it affected religious development in England and America, especially through its influence on John and Charles Wesley and Methodism. In the Scandinavian countries, Pietism, with the support of the nobility and the monarchy, revitalized the Church. Eclipsed for a time by the Enlightenment, Pietism reappeared in the 19th century and became important in the Christian Church. Modern Pietists place emphasis on an ecumenical spirit, the “kingdom of God” and its realization in history, ethics, and personal Christian experience.