Son of Perdition is a term used by The Church of Jesus Christ of Latter-day Saints (sometimes referred to as Mormons) to describe a person who will not take any part in the glory of God in the afterlife. This is in contrast to most people, who will receive a "kingdom of glory" after the Final Judgment, and enter into either the Celestial, Terrestrial, or Telestial Kingdom. A Son of Perdition will be cast into what is commonly called Outer darkness. Joseph Smith, the first LDS Church president called the name of the place Gnolom or Gnolaum (depending on spelling from available transcripts).

According to LDS theology, there are two classes of persons who will become sons of perdition:

1. The pre-mortal hosts (or followers) of Satan. It is taught that, in the pre-mortal life, they chose to follow a plan proposed by Satan, rather than God and Jesus' plan.
2. Those in mortal life who "deny the Holy Ghost," which is generally interpreted as leaving and fighting against the LDS Church after receiving a personal witness of the truthfulness of the Gospel from the Holy Ghost. It is frequently—though not universally—added that a son of perdition must have a "perfect knowledge" of the truth of the Church (mere faith is not enough). Generally, the requirement of perfect knowledge is only fulfilled by a personal visitation from Jesus Christ or an angel of the Lord. This was taught by LDS Church President Spencer W. Kimball.

In Doctrine and Covenants 88:24 (text), they are described as inhabiting "a kingdom which is not a kingdom of glory." The most comprehensive exposition of the phrase can be found in Section 76 in the Doctrine and Covenants (text).

Son of Perdition is also a name for Antichrist (2 Thessalonians 2:3)