The Fundamentalist Church of Jesus Christ of Latter Day Saints
From MormonWiki
According to President Hinckley there should be no such thing as Mormon fundamentalists, since this last word is usually associated with intolerant behaviors. 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 true LDS Church renounced polygamy.