The Mormon pioneers were members of the Church of Jesus Christ of Latter-day Saints, also known as Latter-day Saints, who migrated beginning in the mid-1840s until the late-1860s across the United States from the Midwest to the Salt Lake Valley in what is today the U.S. state of Utah. At the time of the planning of the exodus in 1846, the territory comprising present-day Utah was part of the Republic of Mexico, with which the U.S. soon went to war over a border dispute left unresolved after the annexation of Texas. The Salt Lake Valley became American territory as a result of the Treaty of Guadalupe Hidalgo, which ended the war.

The Church of Jesus Christ of Latter-day Saints, informally known as the LDS Church or Mormon Church, is a restorationist, nontrinitarian Christian denomination that is the largest denomination in the Latter Day Saint movement. The church is headquartered in the United States in Salt Lake City, Utah and has established congregations and built temples worldwide. According to the church, it has over 17 million members and over 99 thousand volunteer missionaries. As of 2012, the church was the fourth-largest Christian denomination in the U.S. As of 2023, the church reported over 6.8 million U.S. members.