According to President Hinckley there is no such thing as a "Mormon fundamentalist," since this implies that the person somehow adheres more fully to the principles of The Church of Jesus Christ of Latter-day Saints than its actual members, which such a person is not. However, members of a splinter group of the official Church of Jesus Christ of Latter-day Saints call themselves The Fundamentalist Church of Jesus Christ of Latter Day Saints (FLDS). It is the world's largest group of such type; it may also be America's largest practitioner of plural marriage. The FLDS Church is not affiliated with The Church of Jesus Christ of Latter-day Saints (LDS), from which it split in the late 1890s after the LDS Church renounced polygamy. The separate FLDS society is centered on the border of Utah and Arizona. There has been no individual ownership of the property, as the sect itself holds all property for distribution. Litigation is under way to try to reassign property rights to individuals. In this fundamentalist creed, polygamy is practiced. Those who practice it are fundamentalists, apart from and distinct from anyone known as a Mormon.
- Until 2007, the church was led by Warren Jeffs, who succeeded his father Rulon Jeffs in 2002. For nearly two years, Warren Jeffs had been wanted on sex-crimes charges; and from May 2004 until his arrest in August 2006 he was on the FBI's Ten Most-Wanted List. On September 25, 2007, Jeffs was found guilty of two counts of being an accomplice to rape and was sentenced to ten years to life in prison. He formally resigned as the president of the FLDS Church on November 20, 2007.
- See the article on "Mormon" Polygamy.
-  Video of Mike Otterson's Public Affairs' statement about the Texas fundamentalist sect.