Mormon fundamentalism (also called
fundamentalist Mormonism) is a 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 and
Brigham Young, the first two
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 (members of the LDS Church). The principle most often associated with Mormon fundamentalism is
plural marriage, a form of
polygyny first taught by
Joseph Smith, the founder of the
Latter Day Saint movement. 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. Today, the LDS Church excommunicates any of its members who practice plural marriage or who otherwise closely associate themselves with Mormon fundamentalist practices.