Joseph Smith, Jr. (December 23, 1805 – June 27, 1844) was the founder of the Latter Day Saint movement, also known as Mormonism, and an important religious and political figure in the United States during the 1830s and 1840s. In 1827, Smith began to gather a religious following after announcing that an angel had shown him a set of golden plates describing a visit of Jesus to the indigenous peoples of the Americas. In 1830, Smith published what he said was a translation of these plates as the Book of Mormon. The same year he organized a new church, which he called the Church of Christ.

During most of the 1830s, Smith lived in Kirtland, Ohio, which remained the headquarters of the church until the collapse of the Kirtland Safety Society encouraged him to gather the church to the Latter Day Saint settlement in Missouri. There, tensions between church members and non-Mormons escalated into the 1838 Mormon War, leading to Smith's imprisonment and an executive order by the Missouri governor that effectively expelled Latter Day Saints from the state. After escaping from custody, Smith and his followers settled in Nauvoo, Illinois.

There he was accused of aspiring to create a theocracy and of practicing polygamy, which he publicly denied. He ran for President of the United States in 1844, and during the campaign, his part in the Nauvoo City Council's decision to suppress a newspaper that had published accusations against Smith led to his assassination by a mob of non-Mormons.

Joseph Smith's legacy includes several religious denominations with adherents numbering in the millions, denominations that share a belief in Jesus but that vary in their acceptance of each other and of traditional Christianity. Smith's followers consider him a prophet and believe that some of his revelations are sacred texts on par with the Bible.