Mormon fundamentalism

Mormon fundamentalism (also called fundamentalist Mormonism) is a variant of Christian fundamentalism with belief in the validity of selected fundamental aspects of Mormonism as taught and practiced in the nineteenth century, particularly during the administrations of Joseph Smith, Brigham Young, and John Taylor, the first three presidents of the Church of Jesus Christ of Latter-day Saints (LDS Church). Mormon fundamentalists seek to uphold tenets and practices no longer held by mainstream Mormons. The principle most often associated with Mormon fundamentalism is plural marriage, a form of polygamy first taught in the Latter Day Saint movement by the movement's founder, Smith. A second and closely associated principle is that of the United Order, a form of egalitarian communalism. Mormon fundamentalists believe that these and other principles were wrongly abandoned or changed by the LDS Church in its efforts to become reconciled with mainstream American society.

There is no single authority accepted by all Mormon fundamentalists; viewpoints and practices of individual groups vary. Fundamentalists have formed numerous small sects, often within cohesive and isolated communities throughout the Mormon Corridor in the Western United States, Western Canada, and northern Mexico. Sources estimate the number of North American adherents to be between 20,000 and 60,000, with about half of those living in polygamous households. One 2020 source estimated that about 75% of North American Mormon fundamentalists were affiliated with either the Fundamentalist Church of Jesus Christ of Latter Day Saints (FLDS), Apostolic United Brethren (AUB or Allred Group), or Latter Day Church of Christ (DCCS or Kingston Group).

Founders of mutually rival Mormon fundamentalist denominations include Lorin C. Woolley, John Y. Barlow, Joseph W. Musser, Leroy S. Johnson, Rulon C. Allred, Elden Kingston, and Joel LeBaron. The largest Mormon fundamentalist groups are the Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS Church) and the Apostolic United Brethren (AUB).