People should no longer use the word "Mormon" to characterise the faith, the head of the Utah-based church has said.
Church leader Russell Nelson urged both followers and non-followers to stick to the official designation "the Church of Jesus Christ of Latter-day Saints".
Mr Nelson, 93, said the move had been prompted by God, who "impressed upon my mind the importance of the name".
However, he added, the central text of the Church would still be called the Book of Mormon.
The church's updated online guide says the terms "Mormon Church", "Mormons" and "Mormonism" are no longer acceptable.
It also bans the abbreviation "LDS" as shorthand for the faith.
For the followers of the church, the president is also a prophet who receives divine revelations.
Among the faith's followers is 2012 US Republican presidential candidate Mitt Romney.
Members of the church worship Jesus Christ, but have substantial differences in belief to the Catholic, Protestant, and Orthodox Christian denominations.