Sidney Rigdon (19 February 1793 - 14 July 1876) was an important figure in the early history of the Church of Jesus Christ of Latter-Day Saints. He delivered many important sermons, and some critics argue Rigdon's influence was as strong as that of church founder Joseph Smith. His close relationship with Smith deteriorated, and Rigdon was eventually excommunicated.

From his mid-twenties, Rigdon was a popular Reformed Baptist preacher in Ohio.

He encountered Mormon missionaries, including Parley P. Pratt and was baptised into the religion, along with over one thousand of his congregation. In December of 1830, he met Joseph Smith.

Rigdon initially served as scribe for Smith. In 1833 Rigdon was named as a counselor to Smith. He served as a counselor until the Smith's death in 1844, although he was estranged from the presidency for most of the mid 1840s

In Oct 1838, Rigdon, Smith and others were imprisoned in Liberty, Missouri. They were often abused, and Rigdon's health deteriorated.

After Smith's murder in 1844, Rigdon was one of several who claimed leadership of the faith. Most Mormons regarded Brigham Young as Smith's only legitimate successor.