Today, the practice of polygamy is strictly prohibited in the Church, as it has been for over a century. Polygamy — or more correctly polygyny, the marriage of more than one woman to the same man — was a part of the teachings of The Church of Jesus Christ of Latter-day Saints for a half-century. The practice began during the lifetime of Joseph Smith but became publicly and widely known during the time of Brigham Young.
In addition to the information on this page, see comprehensive essays on LDS.org:
Plural Marriage in Kirtland and Nauvoo
Plural Marriage and Families in Early Utah
The Manifesto and the End of Plural Marriage
In 1831, Church founder Joseph Smith made a prayerful inquiry about the ancient Old Testament practice of plural marriage. This resulted in the divine instruction to reinstitute the practice as a religious principle.
Latter-day Saint converts in the 19th century had been raised in traditional, monogamous homes and struggled with the idea of a man having more than one wife. It was as foreign to them as it would be to most families today in the western world, and even Brigham Young, who was later to have many wives and children, confessed to his initial dread of the principle of plural marriage.
Subsequently, in 1890, President Wilford Woodruff, fourth president of the Church, received what Latter-day Saints believe to be a revelation in which God withdrew the command to practice plural marriage. He issued what has come to be known as the "Manifesto," a written declaration to Church members and the public at large that stopped the practice of plural marriage.
Today Church members honor and respect the sacrifices made by those who practiced polygamy in the early days of the Church. However, the practice is banned in the Church, and no person can practice plural marriage and remain a member.
The standard doctrine of the Church is monogamy, as it always has been, as indicated in the Book of Mormon (Jacob, chapter 2): “Wherefore, my brethren, hear me, and hearken to the word of the Lord: For there shall not any man among you have save it be one wife; and concubines he shall have none. … For if I will, saith the Lord of Hosts, raise up seed unto me, I will command my people; otherwise they shall hearken unto these things.”
In other words, the standard of the Lord’s people is monogamy unless the Lord reveals otherwise. Latter-day Saints believe the season the Church practiced polygamy was one of these exceptions.
Polygamous groups and individuals in and around Utah often cause confusion for casual observers and for visiting news media. The polygamists and polygamist organizations in parts of the western United States and Canada have no affiliation whatsoever with The Church of Jesus Christ of Latter-day Saints, despite the fact that the term "Mormon" — widely understood to be a nickname for Latter-day Saints — is sometimes incorrectly applied to them.