The unofficial term Limbo /ˈlɪmboʊ/ (from Latin limbus 'edge, boundary', referring to the edge of Hell) is the afterlife condition in medieval Catholic theology, of those who die in original sin without being assigned to the Hell of the Damned. However, it has become the general term to refer to nothing between time and space in general.

Some medieval theologians of Western Europe described the underworld ("hell", "hades", "infernum") as divided into three distinct parts: Hell of the Damned, Limbo of the Fathers or Patriarchs, and Limbo of the Infants.

The Limbo of the Fathers is the state or place for people who were friends of God but died before the death of Jesus Christ; when Jesus died he descended into hell and rescued the souls of those who had died before him: this is traditionally known as the harrowing of hell.

The Limbo of the Infants was the hope that just because a child died before baptism, it does not mean they deserve punishment (or are developed enough to be cognizant of separation from God), though they cannot have full salvation (or experience the Beatific Vision.) The Limbo of the Infants is neither affirmed nor denied by Catholic doctrine.

The "Limbo of the Patriarchs" or "Limbo of the Fathers" (Latin limbus patrum) is seen as the temporary state of those who, despite the sins they may have committed, died in the friendship of God but could not enter heaven until redemption by Jesus Christ made it possible. The term Limbo of the Fathers was a medieval name for the part of the underworld (Hades) where the patriarchs of the Old Testament were believed to be kept until Christ's soul descended into it by his death through crucifixion and freed them.

The Catechism of the Catholic Church describes Christ's descent into Hell as meaning primarily that "the crucified one sojourned in the realm of the dead prior to his resurrection. This was the first meaning given in the apostolic preaching to Christ's descent into Hell: that Jesus, like all men, experienced death and in his soul joined the others in the realm of the dead." It adds: "But he descended there as Saviour, proclaiming the Good News to the spirits imprisoned there." It does not use the word Limbo.

This concept of Limbo affirms that admittance to heaven is possible only through the intervention of Jesus Christ, but does not portray Moses, etc. as being punished eternally in Hell. The concept of Limbo of the Patriarchs is not spelled out in Scripture, but is seen by some^[who?] as implicit in various references:

According to Saint Thomas Aquinas, unlike Purgatory and Hell, in the Limbo of Patriarchs there was not the penalty of sense (the affliction by fire in which the soul burns after death and also the body after the resurrection of the flesh), but solely the penalty of harm, which is the privation of the beatific vision of God. However, the souls in Limbo of Patriarchs enjoyed the natural knowledge of God and experienced great joy because of the future glory that awaited them in Paradise.