The original Nauvoo Temple of the Latter-day Saint movement built in Nauvoo, Illinois.

The Latter Day Saint movement is a religious movement founded primarily by Joseph Smith, Jr. in the early 19th century. It is strongly restorationist, intending to transcend Protestant denominationalism by restoring what they consider to be a form of Christianity more true to the New Testament. The Latter Day Saint movement was first known as the Church of Christ, and eventually spawned many religious denominations including The Church of Jesus Christ of Latter-day Saints and the Community of Christ. A minority of these denominations refer to their doctrines, practices, and cultures as Mormonism, but others find the term inaccurate or offensive.

The Latter Day Saint movement began in the late 1820s in western New York while Joseph Smith, Jr. was dictating what he said was the translation of a book of Golden Plates buried centuries ago by a nation of pre-Columbian Christians. The movement grew rapidly after this book was published in 1830 as the Book of Mormon and used by missionaries as a proselytizing tool. After a succession crisis, many of the Latter Day Saints emigrated to what was then Mexico (now Utah) to establish a new colony led by Brigham Young. Other smaller groups established organizations in Missouri, Illinois, Michigan, and Pennsylvania, many of which united around Smith's son Joseph Smith III in 1860 in Missouri. Most Latter Day Saint denominations existing today have some historical relationship with either of these two groups.