Assistant President of the Church (also referred to as Associate President of the Church) was a position in the leadership hierarchy in the early days of the Latter Day Saint church founded by Joseph Smith. The Assistant President was the second-highest authority in the church and was a member of the church's governing First Presidency. As President of the Church, Smith appointed two (possibly three) men to serve in the position of Assistant President. After Smith's death, most Latter Day Saint denominations discontinued the position of Assistant President of the Church.
On December 5, 1834, Smith ordained Oliver Cowdery to be his "assistant-president". The minutes of this meeting state that Smith said the following words after laying his hands on Cowdery's head: "In the name of Jesus Christ, who was crucified for the sins of the world, I lay my hands upon thee and ordain thee an assistant-president to the High and Holy Priesthood, in the Church of the Latter-day Saints."
At the organization of the church in 1830, Cowdery had been designated the "second elder" of the church. After Smith organized the First Presidency in 1832, Cowdery's standing in the church hierarchy had become uncertain. Cowdery's ordination as Assistant President reaffirmed his status as second only to Smith in church authority.
After Cowdery's ordination, Smith explained the purpose of the position of Assistant President:
The office of Assistant President is to assist in presiding over the whole Church, and to officiate in the absence of the President, according to his rank and appointment .... The office of this priesthood is also to act as spokesman, taking Aaron for an example. The virtue of the above priesthood is to hold the keys of the kingdom of heaven or of the Church militant.
As holder of the keys of the priesthood, the Assistant President of the Church was intended to be the person who would succeed to the presidency of the church upon the death of Smith. The Assistant President ranked higher than the counselors in the First Presidency and the President and members of the Quorum of the Twelve Apostles. Like the members of the First Presidency and the Twelve, the Assistant President was accepted by the church as a prophet, seer, and revelator. The Assistant President was not ordained to the priesthood office of apostle, but as a holder of all priesthood keys, the authority of apostle was an implied authority of the position.