President of the Quorum of the Twelve Apostles is a priesthood calling in the Church of Jesus Christ of Latter-day Saints (LDS Church). Normally, the president of the Quorum of the Twelve is the most senior apostle in the church, aside from the president of the church. When the president of the church dies, it is the president of the Quorum of the Twelve who becomes the new church president. The calling of President of the Twelve has been held by 27 men (one of whom served two non-consecutive terms). 16 Quorum Presidents have subsequently become President of the Church. Since January 2018, Dallin H. Oaks has been the President of the Quorum of the Twelve. Since Oaks is also first counselor in the First Presidency, M. Russell Ballard served as acting president until his death on November 12, 2023. Jeffrey R. Holland became the new acting president on November 15, 2023.
 Upon the death of the president of the church, the First Presidency automatically dissolves. The Quorum of the Twelve Apostles becomes the highest leadership body and their president becomes the most senior leader of the church. On the death of church president Joseph Smith in 1844, Brigham Young was the Quorum President, and he persuaded the majority of church members that Smith's death left him and not Sidney Rigdon, who had been Smith's first counselor in the First Presidency, as the senior leader of the church. Smith had reportedly taught the apostles, "Where I am not, there is no First Presidency over the Twelve."
 In 1847, the Quorum of the Twelve reconstituted the First Presidency, with Young as church president. During Young's presidency, seniority within the Quorum of the Twelve was formalized to mean "continuous service as an Apostle since being ordained as one of the Twelve".[citation needed] The original apostles of 1835 had been ranked by age, and two of them had been excommunicated and later restored to fellowship. With this rule in place, upon the death of Young, John Taylor led the church, first as Quorum President and, after 1880, as President of the Church. Wilford Woodruff became President of the Twelve.
 After Taylor died in 1887, Woodruff did not reorganize the First Presidency until 1889. But before his own death in 1898, he advised the Quorum of the Twelve that "in all future time, when the president of the church should die and thereby the First Presidency become disorganized, it would be the duty of the proper authorities of the church to proceed at once without any unnecessary delay, to reorganize the First Presidency." Snow followed this advice and since then every interval between the death of the president of the church and the ordination of a new president has been less than two weeks, long enough to complete the funeral services and allow for the Quorum of the Twelve to nominate and sustain the president of the twelve as the new church president. When the president of the twelve becomes the president of the church, the next apostle in seniority becomes the new president of the twelve.
 The president of the Quorum of the Twelve Apostles is the priesthood leader of the members of the quorum. As such, all members of the quorum report directly to him. The president's other duties consist of presiding at and conducting weekly meetings of the quorum in the Salt Lake Temple; making decisions about the particular assignments to be made to the members of the quorum; speaking on behalf of the quorum to members of the church and the media; scheduling twice-annual conferences for each stake and district in the church; and acting as a liaison in coordinating the work of the quorum with the First Presidency, the Quorums of the Seventy, and the Presiding Bishopric.
 When adherents refer to the president of the Quorum of the Twelve, his name is usually prefaced by the honorific title "President".
 If the president of the Quorum of the Twelve Apostles is serving as a counselor in the First Presidency, he retains that title but is not numbered among the twelve. The most senior apostle who is not in the First Presidency is then named as Acting President of the Quorum of the Twelve Apostles. The acting president assumes all of the duties that would normally rest upon the president of the quorum. The title of Acting President was first used in 1918 for Rudger Clawson. The position has also been used during times of infirmity of a president of the twelve: for example, Howard W. Hunter was Acting President for the infirm Marion G. Romney from 1985 to 1988.
 Boyd K. Packer was the acting president of the Quorum of the Twelve Apostles from 1994 to 2008 when Gordon B. Hinckley and Thomas S. Monson were presidents of the quorum but were serving in the First Presidency.
 On January 16, 2018, the church announced that due to the call of Dallin H. Oaks as a counselor in the First Presidency, M. Russell Ballard would serve as Acting President. After Ballard's death on November 12, 2023, Jeffrey R. Holland was set apart as the new acting president on November 15.
 He previously served as Acting President when the more senior apostles, Gordon B. Hinckley (1994-1995) and Thomas S. Monson (1994-1995 and 1995-2008), were members of the First Presidency.