Radical Pietism are those Christian churches who decided to break with denominational Lutheranism in order to emphasize certain teachings regarding holy living. Radical Pietists contrast with Church Pietists, who chose to remain within their Lutheran denominational settings. Radical Pietists distinguish between true and false Christianity and hold that the latter is represented by established churches. They separated from established churches to form their own Christian denominations.

Radical Pietism emphasizes the need for a "religion of the heart" instead of the head, and is characterized by ethical purity, inward devotion, charity, asceticism, and mysticism. Leadership was empathetic to adherents instead of sacramentalism. The Pietistic movement developed in Germany, led by those who believed a deeper emotional experience was incompatible with what they saw as a preset adherence to form, no matter how genuine. They stressed a personal experience of salvation and a continuous openness to new spiritual illumination.

Many of the Radical Pietists are influenced by the writings of Jakob Böhme, Gottfried Arnold, and Philipp Jakob Spener, among others. They teach that personal holiness (piety), spiritual maturity, Bible study, prayer, and fasting are essential toward "feeling the effects" of grace.

Churches in the Radical Pietist movement include the Mennonite Brethren Church, Community of True Inspiration (Inspirationalists), the Baptist General Conference, members of the International Federation of Free Evangelical Churches (such as the Evangelical Covenant Church and the Evangelical Free Church), the Templers, the River Brethren (inclusive of the Brethren in Christ Church, the Calvary Holiness Church, the Old Order River Brethren and the United Zion Church), as well as the Schwarzenau Brethren.