Hyrum Smith (February 9, 1800 – June 27, 1844) was the older brother of Joseph Smith, Jr. and a leader in the early Latter Day Saint movement. Hyrum was born in Turnbridge, Vermont, the second son of Joseph Smith, Sr. and Lucy Mack Smith. Hyrum received a limited education, and established himself as a farmer. He married Jerusha Barden (1805–1837), on November 2, 1826, and had four daughters and two sons. After Jerusha's death, he married Mary Fielding in 1837, with whom he had a son, Joseph Fielding, and a daughter Martha. In August 1843 he married his second wife's sister Mercy Fielding Thompson, widow of Times and Seasons editor Robert B. Thompson, and Catherine Phillips, as plural wives.
As the church headquarters and membership moved west, Hyrum and his family relocated. In 1831, he established a home in Kirtland, Ohio. During his residence there, he served as foreman of the quarry providing stone for the Kirtland Temple. Between 1831 and 1833, he served proselyting missions to Missouri and Ohio. In 1834, under the direction of Joseph Smith, he recruited members for a militia, Zion's Camp, and traveled with the group to the aid of the Latter Day Saints in Missouri. He was appointed Second Counselor in the church's First Presidency in November 1837. In 1838 and 1839, Hyrum, Joseph and three other church leaders shared a jail cell in Liberty, Missouri while awaiting trial.
After relocating to Nauvoo, Illinois, Hyrum was ordained as Presiding Patriarch of the Church, a position formerly held by his deceased father, Joseph Smith, Sr. He also was ordained by Joseph to the priesthood office of Apostle and replaced Oliver Cowdery as Assistant President of the Church; in this capacity, Hyrum acted as President of the Church in Joseph's absence and was designated to be Joseph's successor if he were killed or incapacitated.
When warned of possible danger, Joseph urged Hyrum and his family to flee to Cincinnati, Ohio. Hyrum refused and, in 1844, traveled with Joseph to Carthage, Illinois where both were charged with riot and treason. Joseph, Hyrum, John Taylor and Willard Richards were held awaiting trial in a jail in Carthage. On June 27, 1844, the building was attacked by a mob of between sixty to two hundred men. While attempting to barricade the door to prevent the mob from entering, Hyrum was shot in the face and killed instantly. Taylor was struck by several bullets but survived with the help of Richards. Joseph was killed by at least two shots, and fell through a second story window to the ground where he was shot again.
Because of his position as Assistant President of the Church, it is likely that Hyrum would have succeeded Joseph and become the next president of the Church of Jesus Christ of Latter Day Saints had he outlived his brother.