Pioneer Day is an official holiday celebrated on July 24 in the American state of Utah, with some celebrations taking place in regions of surrounding states originally settled by Mormon pioneers. It commemorates the entry of Brigham Young and the first group of Mormon pioneers into the Salt Lake Valley on July 24, 1847, where the Latter-day Saints settled after being forced from Nauvoo, Illinois, and other locations in the eastern United States. Parades, fireworks, rodeos, and other festivities help commemorate the event. Similar to July 4, many local and all state-run government offices and many businesses are closed on Pioneer Day.

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.