The concept of premortal life in the Latter Day Saint movement is an early and fundamental doctrine which states that all people existed as spirit bodies before coming to Earth and receiving a mortal body. In Mormonism's eponymous text, the Book of Mormon, published in 1830, the premortal spirit of Jesus Christ appears in human form and explains that individuals were created in the beginning in the image of Christ. In 1833, early in the Latter Day Saint movement, its founder Joseph Smith taught that human souls are co-eternal with God the Father just as Jesus is co-eternal with God the Father, "Man was also in the beginning with God. Intelligence, or the light of truth, was not created or made, neither indeed can be."

Shortly before his death in 1844, Smith elaborated on this idea in his King Follett discourse: ...the soul—the mind of man—the immortal spirit. Where did it come from? All learned men and doctors of divinity say that God created it in the beginning; but it is not so: the very idea lessens man in my estimation...[The Bible] does not say in the Hebrew that God created the spirit of man. It says, "God made man out of the earth and put into him Adam's spirit, and so became a living body." The mind or the intelligence which man possesses is co-equal with God himself...Is it logical to say that the intelligence of spirits is immortal, and yet that it has a beginning? The intelligence of spirits had no beginning, neither will it have an end. That is good logic. That which has a beginning may have an end. There never was a time when there were not spirits; for they are co-equal with our Father in heaven.

Boyd K. Packer, of the Quorum of the Twelve Apostles of the Church of Jesus Christ of Latter-day Saints (LDS Church), the largest denomination in the Latter Day Saint movement, taught, "that we are the children of God, that we lived with him in spirit form before entering mortality."

In the context of this core Latter Day Saint doctrine, the term premortal existence is a more accurate term to describe the time before this mortal existence than pre-existence, since pre-existence has a connotation of something existing before any existence, and Latter Day Saint doctrine specifically rejects ex-nihilo creation. Therefore, the term premortal existence is strongly preferred in the LDS Church, representing the time before this mortal life. However, the term pre-existence is in widespread use.

LDS Church After Smith's death, and a six-month succession crisis, the majority of Smith's adherents followed Brigham Young who renamed the church to the LDS Church and led followers to what would become Utah Territory. The doctrine of premortal existence was elaborated by some other leaders within the LDS Church. Although the mind and intelligence of humanity were still considered to be co-eternal with God, and not created, Young taught that the spirit was different from the mind or intelligence, resolving the seeming conflict between Book of Mormon verses indicating God was creator and Smith's later teaching that all individuals were co-eternal with God. Young postulated that we each had a pre-spirit intelligence that later became part of a spirit body, which then eventually entered a physical body and was born on earth. In 1857, Young stated that every person was "a son or a daughter of [the Father]. In the spirit world their spirits were first begotten and brought forth, and they lived there with their parents for ages before they came here."

In the LDS Church the idea of spirit birth was described in its modern doctrinal form in 1909, when the church's First Presidency issued the following statement:

This description is widely accepted by modern Latter-day Saints as fundamental to the plan of salvation. However, there are differences of opinion as to the nature of the premortal existence in other Latter Day Saint denominations.

The LDS Church teaches that during the premortal existence, there was a learning process which eventually led to the next necessary step in the premortal spirits' opportunity to progress. This next step included the need to gain a physical body that could experience pain, sorrow and joy and "walk by faith". According to this belief, these purposes were explained and discussed in councils in heaven, followed by the War in Heaven where Satan rebelled against the plan of Heavenly Father.

In the 1840s, Joseph Smith stated that the human spirit existed with God before the creation of Earth. Thus, Latter-day Saints believe in a pre-mortal existence, in which people are literally the spirit children of God, though Smith is explicitly quoted in the King Follett Sermon as saying that "God never had the power to create the spirit of man." Latter-day Saints often point to Jeremiah 1:5 as one example of evidence in the Bible for a pre-earth existence.In this section Jeremiah the prophet is told that the Lord knew him before He formed him in the belly and before he came out of the womb and was sanctified and ordained to be a prophet at that time. This teaching is primarily based, however, upon revealed doctrine by Smith and his successors to the presidency of the LDS Church. Prior to the existence of spirits, some element of the human spirit, called intelligence, existed eternally in the same sense that God existed eternally, but in a less progressed form of energy or matter. This may explain the church's teaching that man and God are co-eternal (carefully distinguishing "co-eternal" from "equal", which is not a part of Mormon doctrine). Within Latter-day beliefs, Jesus Christ is looked upon as the creator of the Earth under God the Father's direction, while God the Father is the creator of all men, women, and creatures of the Earth.

God before the Earth's creation

According to Mormon theology, God the Father is a physical being of "flesh and bones." Latter-day Saints identify him as the biblical god Elohim. Latter-day Saint leaders have also taught that God the Father was once a mortal man who has completed the process of becoming an exalted being. According to Joseph Smith, God "once was a man like one of us and[...] once dwelled on an earth the same as Jesus Christ himself did in the flesh and like us.".

Adam-God doctrine

A now reversed teachings by top leaders about God in the pre-existence is the Adam–God doctrine taught in the temple into the 1900s. This now-rejected teaching stated that Heavenly Father was a man from another planet who became exalted and then as the god-archangel Michael formed the Earth and then took one of his wives and became the mortals Adam and Eve. After death they returned to their state of immortal Heavenly Parents.

Spirit intelligences and God's spirit children

It is believed there were pre-existing "spirit intelligences" that existed before God the Father and Heavenly Mother created spiritual bodies for them: "self-existing intelligences were organized into individual spirit beings" by the Heavenly Parents and they became the "begotten sons and daughters of God". The procreative process whereby the intelligences became spirits has not been explained. While spirit bodies are composed of matter, they are described as being "more fine or pure" than regular matter. The first-born spirit child of God the Father was Jehovah, whom Latter-day Saints identify as the premortal Jesus.. Jehovah was a God and was like God the Father in attributes,John 14:6–9. but he did not have an immortal physical body like God the Father until his resurrection.Ether 3:14–17.

Council in Heaven

God the Father's plan for all his children was to provide a way for them to become more like him. Although they were happy living in heaven with God the Father, God's spirit children could not experience the "fulness of joy" enjoyed by him unless their spirit bodies were joined with a physical body. God the Father convened a "Grand Council" of all his children to propose a plan of progression, known to Latter-day Saints as the plan of salvation. According to the proposed plan, God would provide an earth where spirit children could receive a physical body.

One of the purposes of this earthly existence is for each of God's children to demonstrate through free will the desire to choose righteousness rather than evil. To facilitate free will decision-making, God would cause each spirit child to have no memory of their pre-earth life. All would be given trials and would fall short of perfection, but a savior would be provided, the acceptance of whom would lead ultimately to redemption and a return to live with God the Father forever. Jehovah volunteered to be the savior. and said, "Father, thy will be done, and the glory be thine forever." Jehovah was "the only person who could be [the] Savior". During this pre-mortal existence, God the Father presented the following plan to His children:

Human beings would be born on Earth. There they would receive a physical body necessary to exaltation and a fullness of joy. On earth, they would be tested through trials of their faith, and be subject to mortality. A "veil" would be set in place to obscure humankind's memory of its divine origins, thus allowing for "walking by faith" and for greater freedom of choice by enabling individuals to make their own decisions. LDS Church members believe that only those who live good lives, prove themselves obedient to Heavenly Father's commandments, receive the ordinances of salvation, and repent of their sins will be able to return to Heavenly Father's presence (The Celestial Kingdom). However, because each person's experience in mortality is unique, every individual will be judged in accordance with the opportunities, knowledge, and blessings they had while living on Earth.

Agency

Integral to God's plan was freedom of choice, which God the Father considered an inviolable right of all his children; every individual would have opportunities to make certain choices that would determine the course of their life on Earth and in the hereafter. No human would ever have their freedom taken away in an attempt to force righteous behavior. People would be free to do evil and good, both to themselves and to those around them. Because such freedom would make it possible for God the Father's children to break commandments and sin, a Savior would be needed to offer them freedom from the just consequences of their sins and allow them to repent: this figure would have to overcome both sin and death, making it possible for obedient and repentant individuals to return to Heavenly Father's presence through a plan of mercy. The pre-mortal Jesus Christ, then known as Jehovah, volunteered to be this Savior, agreeing to take upon himself infinite suffering for every sin, mistake, and all pain and suffering ever to be experienced throughout all time by all of God's children. He also agreed to die and be resurrected, thus making it possible for all individuals (obedient or not) to be resurrected. The Holy Spirit would be sent to encourage righteous behavior and guide human beings towards Jesus Christ and Heavenly Father, but would never interfere with freedom.

Also part of the plan was a foreordination of prophets and teachers who would have gifts and callings among men to teach and re-teach correct principles so that freedom could be used wisely. Heavenly Father stressed the important role parents would have to teach their children the path of righteousness and happiness,Deuteronomy 6:7 and the blessing of the holy scriptures that would give a foundation of gospel knowledge, including the knowledge of the saving role of Jesus Christ and the importance of ordinances and covenants in the gospel.