Pietism (), also known as Pietistic Lutheranism, is a movement within Lutheranism that combines its emphasis on biblical doctrine with an emphasis on individual piety and living a holy Christian life.

Although the movement is aligned with Lutheranism, it has had a tremendous impact on Protestantism worldwide, particularly in North America and Europe. Pietism originated in modern Germany in the late 17th century with the work of Philipp Spener, a Lutheran theologian whose emphasis on personal transformation through spiritual rebirth and renewal, individual devotion, and piety laid the foundations for the movement. Although Spener did not directly advocate the quietistic, legalistic, and semi-separatist practices of Pietism, they were more or less involved in the positions he assumed or the practices which he encouraged.

Pietism spread from Germany to Switzerland and the rest of German-speaking Europe, to Scandinavia and the Baltics (where it was heavily influential, leaving a permanent mark on the region's dominant Lutheranism, with figures like Hans Nielsen Hauge in Norway, Peter Spaak and Carl Olof Rosenius in Sweden, Katarina Asplund in Finland, and Barbara von Krüdener in the Baltics, and to the rest of Europe. It was further taken to North America, primarily by German and Scandinavian immigrants. There, it influenced Protestants of other ethnic and other (non-Lutheran) denominational backgrounds, contributing to the 18th-century foundation of evangelicalism, an interdenominational movement within Protestantism that today has some 300 million followers.

In the middle of the 19th century, Lars Levi Laestadius spearheaded a Pietist revival in Scandinavia that upheld what came to be known as Laestadian Lutheran theology, which is adhered to today by the Laestadian Lutheran Churches as well as by several congregations within other mainstream Lutheran Churches, such as the Evangelical Lutheran Church of Finland. The Eielsen Synod and Association of Free Lutheran Congregations are Pietist Lutheran bodies that emerged in the Pietist Lutheran movement in Norway, which was spearheaded by Hans Nielsen Hauge. In 1900, the Church of the Lutheran Brethren was founded and it adheres to Pietist Lutheran theology, emphasizing a personal conversion experience. The Ethiopian Evangelical Church Mekane Yesus, a Lutheran denomination with a largely Pietistic following with some Presbyterian and Pentecostal influence and primarily based in Ethiopia and among the Ethiopian diaspora, is the largest individual member Lutheran denomination within the Lutheran World Federation.

Whereas Pietistic Lutherans stayed within the Lutheran tradition, adherents of a related movement known as Radical Pietism believed in separating from the established Lutheran Churches. Some of the theological tenets of Pietism also influenced other traditions of Protestantism, inspiring the Anglican priest John Wesley to begin the Methodist movement and Alexander Mack to begin the Anabaptist Schwarzenau Brethren movement.

Pietism (in lower case spelling) is also used to refer to an "emphasis on devotional experience and practices", or an "affectation of devotion", "pious sentiment, especially of an exaggerated or affected nature", not necessarily connected with Lutheranism or even Christianity.