Mormonism is a term used to describe the religious, ideological and cultural elements of certain branches of the Latter Day Saint movement, and specifically, The Church of Jesus Christ of Latter-day Saints (LDS Church).

The term derives from the word Mormon, which was originally used as a pejorative term to describe those who believed in the Book of Mormon, a sacred text that adherents believe to be "another testament of Jesus Christ" and testifies of the Bible as part of the religion's canon. Today, Mormonism is properly used in reference to the LDS Church; however, several smaller denominations, and sects of Mormon fundamentalism also embrace the term despite opposition by the LDS Church. Most other Latter Day Saint movement denominations reject use of the term in reference to their faith, and such usage is now rare even though the term was used in the past.