A mortal sin (Latin: peccātum mortāle), in Christian theology, is a gravely sinful act which can lead to damnation if a person does not repent of the sin before death. It is alternatively called deadly, grave, and serious; the concept of mortal sin is found in both Catholicism and Lutheranism.^[1][2] A sin is considered to be "mortal" when its quality is such that it leads to a separation of that person from God's saving grace. Three conditions must together be met for a sin to be mortal: "Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent."^[3] The sin against the Holy Spirit and the sins that cry to Heaven for vengeance are considered especially serious.^[4] This type of sin is distinguished from a venial sin in that the latter simply leads to a weakening of a person's relationship with God. Despite its gravity, a person can repent of having committed a mortal sin. Such repentance is the primary requisite for forgiveness and absolution.^[5]

Teaching on absolution from sins is varied somewhat throughout Christian denominations. The teaching for Catholics on the sacrament of confession and the act of contrition for absolution was declared a mandatory catholic belief in the Council of Trent. Confession and Absolution is practiced in Lutheran churches, with it being historically held on Saturdays in preparation for Mass on the Lord's Day.^[6][7]

The term "mortal sin" is thought to be derived from the New Testament of the Bible. Specifically, it has been suggested by Jimmy Buehler from Theocast^[8] that the term comes from 1 John 5:16–17.^[9] In this particular verse, the author of the Epistle writes "There is a sin that leads to death."^{[9][clarification needed]}

The concept is hinted at in some works of the early Fathers of the Church and explicit in others.

In AD 385, Pacian of Barcelona, in his Sermon Exhorting to Penance,^[a] gives contempt of God, murder, and fornication as examples of "mortal" or "capital sins."^[11]

In AD 393, St. Jerome writes:^[11][12]

There are venial sins and there are mortal sins. It is one thing to owe ten thousand talents, another to owe but a farthing. We shall have to give an accounting for an idle word no less than for adultery. But to be made to blush and to be tortured are not the same thing; not the same thing to grow red in the face and to be in agony for a long time. . . . If we entreat for lesser sins we are granted pardon, but for greater sins, it is difficult to obtain our request. There is a great difference between one sin and another.

— Against Jovinianus, 2:30

In the moral theology of Catholicism, a mortal sin requires that all of the following conditions are met:

1. Its subject matter must be grave. (The term "grave sin" is used at times to indicate grave matter, and at times to indicate mortal sin. But it always remains true that the following two conditions are requisite for mortal sin.^[13])
2. It must be committed with full knowledge (and awareness) of the sinful action and the gravity of the offense.
3. It must be committed with deliberate and complete consent.^[14]

The Catechism of the Catholic Church defines grave matter:^[15]

Grave matter is specified by the Ten Commandments, corresponding to the answer of Jesus to the rich young man: "Do not murder, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and your mother." The gravity of sins is more or less great: murder is graver than theft. One must also take into account who is wronged: violence against parents is in itself graver than violence against a stranger.

— CCC 1858

Although the Church itself does not provide a precise list of grave sins or divide actions into grave and venial categories, Church documents do name certain "grave sins" as well as "offenses" and "actions" whose subject-matter is considered to be grave. For example, in the area of human sexuality, the Catechism of the Catholic Church notes that the following actions can involve increased gravity: extramarital sex,^[16] divorce^[17] (but not legitimate separation),^[18] and masturbation.^[19] The sins against the Holy Spirit and the sins that cry to Heaven for vengeance are considered especially serious.^[4] Further, Pope Francis and many bishops privately regard certain sins as mortal, for example child abuse or neglect of one's parents.^[20][21][22]

With respect to a person's full knowledge of a certain act being a grave sin, the Catholic Church teaches that "unintentional ignorance can diminish or even remove the imputability of a grave offense. But no one is deemed to be ignorant of the principles of the moral law, which are written in the conscience of every man. The promptings of feelings and passions can also diminish the voluntary and free character of the offense, as can external pressures or pathological disorders (mental illness). Sin committed through malice, by deliberate choice of evil, is the gravest."^[23] Furthermore, Catholic teaching also holds that "imputability and responsibility for an action can be diminished or even nullified by ignorance, inadvertence, duress, fear, habit, inordinate attachments, and other psychological or social factors."^[23]

Mortal sins must be confessed by naming the specific offence along with how many times it was committed.^[24]

According to the Catholic Church, no person can receive the Eucharist when in a state of mortal sin:^[25]

Anyone who is aware of having committed a mortal sin must not receive Holy Communion, even if he experiences deep contrition, without having first received sacramental absolution, unless he has a grave reason for receiving Communion and there is no possibility of going to confession.

— CCC 1457

Some mortal sins cause automatic excommunication by the very deed itself, for example renunciation of faith and religion, known as apostasy,^[26] desecration of the Eucharistic species,^[27] and "a completed abortion".^[28] Those mortal sins are so serious that the Church through law has made them crimes. The Church forbids the excommunicated from receiving any sacrament (not just the Eucharist) and also severely restricts the person's participation in other Church liturgical acts and offices. A repentant excommunicated person may talk to a priest, usually in a confessional, about their excommunication to arrange for the remission. Remission cannot be denied to someone who has truly repented their actions and has also made suitable reparation for damages and scandal or at least has seriously promised to do so.^[29][30] However, even if excommunicated, a Catholic who has not been juridically absolved is still, due to the irrevocable nature of baptism, a member of the Catholic Church and therefore must still carry out their obligations of fulfilling their duties of attending Mass, Divine Liturgy, etc. on a Holy Day of Obligation, abstaining from meat on the Fridays of Lent, etc., albeit their communion with the Christ and the Church is gravely impaired. "Perpetual penalties cannot be imposed or declared by decree."^[31] However, "the following are expiatory penalties which can affect an offender either perpetually".^[32]

Since the mid-twentieth century, some theologians have taught that a person who lives by a constant attitude of charity is unlikely to fall in and out of God's graces without being profoundly aware of the change. The term "fundamental option" arose and is used in a variety of senses.^[33][34]

Pope John Paul II reaffirmed traditional teaching going back to the Council of Trent in his encyclical Veritatis Splendor, as does the Catechism of the Catholic Church, which states: "The teaching of the Church affirms the existence of hell and its eternity. Immediately after death the souls of those who die in a state of mortal sin descend into hell, where they suffer the punishments of hell, 'eternal fire'." The Catechism then adds: "The chief punishment of hell is eternal separation from God, in whom alone man can possess the life and happiness for which he was created and for which he longs."^[35] However, the Catechism does not by name say a specific person is in Hell, but it does say that "our freedom has the power to make choices for ever, with no turning back."^[36] Most significantly, the Catechism also proclaims that "There are no limits to the mercy of God".^[37] and that "although we can judge that an act is in itself a grave offence, we must entrust judgment of persons to the justice and mercy of God."^[36] One cannot see into their mind to know if it was deliberate or committed in full knowledge. Also, like the father in the Parable of the Prodigal Son, God forgives those who repent sincerely. Vatican II, in its Dogmatic Constitution Lumen Gentium, reflects the traditional teaching of the Church on punishment, and on merit or reward for good deeds.^[38]

Mortal sin is ordinarily remitted by the priestly absolution in the Sacrament of Penance. However, the effectiveness of the absolution is dependent of the acts of the penitent starting with sorrow for sin or contrition. Perfect contrition, coupled with the firm resolution to sin no more and to make recourse to the sacrament of Penance as soon as possible, can restore a person's relationship with God, as well as God's saving grace, that is, sanctifying grace. This teaching on perfect contrition is a reminder that God's mercy and forgiveness is available outside the Sacrament of Penance, yet, also indicates that Catholics who know about Christ's institution of the sacrament of Penance must intend to use it. Any human act that arises from a person's love of God, is inspired by God's prevenient action and is directed to doing as God requires.^[39] When perfect contrition is the means by which one seeks to restore one's relationship with God, there must also be a resolution to confess all mortal sins (that have not been confessed and absolved previously) in the Sacrament of Penance.^[40]

Autonomous, self-governing (Latin: sui iuris), Catholic particular churches and liturgical rites in full communion with the Bishop of Rome, the Pope, are known as Eastern Catholic churches.^[41] They derive their theology and spirituality from some of the same sources as the Eastern Orthodox and Oriental Orthodox churches,^[42] yet use the Latin Catholic distinction between mortal and venial sin. However, names other than mortal and venial are often used.^[43][44][45]

The following is a partial alphabetical list of actions that are defined as constituting grave matter, according to the Catechism of the Catholic Church or like sources (such as declarations by the Congregation for the Doctrine of the Faith, Apostolic Letters, or other sources printed by Church authorities).

In Lutheranism, sins are of two classes:^[2]

As to their effect, sins are divided into mortal sins and venial sins. Mortal sins are those which result in the death of the sinner. This term takes in all the sins of the unbelievers. In the case of the believers those sins are called mortal which force the Holy Spirit to depart from one’s heart, which destroy faith. Venial sins are sins which, though they in themselves merit eternal death, are daily forgiven to the believer. They are also called sins of weakness. They do not drive the Holy Spirit from the heart, do not extinguish faith.^[2]

Venial sins are sins of weakness; they are limited to believers, and do not kill faith, because they are not done intentionally. In themselves they are real sins and are worthy of death, but through faith Christians have forgiveness for them. Mortal sins are such as kill faith and drive the Holy Spirit from the heart, because no man can sin willfully intentionally and at the same time believe in Christ for the forgiveness of his sins.^[100]

The Smalcald Articles of Lutheranism teach that apostasy from the Christian faith can occur through loss of faith or through falling into a lifestyle characterized by mortal sin:^[101]

It is, accordingly, necessary to know and to teach that when holy men, still having and feeling original sin, also daily repenting of and striving with it, happen to fall into manifest sins, as David into adultery, murder, and blasphemy, that then faith and the Holy Ghost has departed from them [they cast out faith and the Holy Ghost]. For the Holy Ghost does not permit sin to have dominion, to gain the upper hand so as to be accomplished, but represses and restrains it so that it must not do what it wishes. But if it does what it wishes, the Holy Ghost and faith are [certainly] not present. For St. John says, 1 John 3:9: Whosoever is born of God doth not commit sin, … and he cannot sin. And yet it is also the truth when the same St. John says, 1:8: If we say that we have no sin, we deceive ourselves and the truth is not in us.^[101]

The Lutheran divine Martin Chemnitz, who contributed to the development of Lutheran systematic theology, delineated what are considered mortal sins:^[102]

For Scripture distinguishes between sins, namely that in the saints or reborn there are some sins because of which they are not condemned, but at the same time retain faith, the Holy Spirit, grace, and the forgiveness of sins. (Rom 7:23–8:1; 1 Jn 1:8–9; Ps 32:1). But Scripture testifies that there are also some other sins in which also the reconciled, when they have fallen, lose faith, the Holy Spirit, the grace of God, and life eternal, and render themselves subject to divine wrath and eternal death unless, turned again, they are reconciled to God through faith (Rom 8:13; 1 Cor 6:10; Gal 5:21; Eph 5:5; Col 3:6; 1 Jn 3:6, 8; 1 Tim 1:19; 2 Per 1:9). And the useful distinction between mortal and venial sin is drawn from this basis.^[102]

With respect to the examination of conscience, Chemnitz implored Lutheran clergy to remind the faithful of what sins are mortal (especially the seven deadly sins) and those that are venial.^[102]

According to Father Allyne Smith, "While the Roman Catholic tradition has identified particular acts as 'mortal' sins, in the Eastern Orthodox tradition we see that only a sin for which we don't repent is 'mortal.'"^[103]

According to the Mission of The Orthodox Church in America, in answer to a parishioner's query:^[104]

In the Orthodox Church there are no "categories" of sin as found in the Christian West. In the pre-Vatican II Catholic catechism, sins were categorized as "mortal" and "venial." In this definition, a "mortal" sin was one which would prevent someone from entering heaven unless one confessed it before death. ...These categories do not exist in the Orthodox Church. Sin is sin. Concerning Confession, having a list of deadly sins could, in fact, become an obstacle to genuine repentance. For example, imagine that you commit a sin. You look on the list and do not find it listed. It would be very easy to take the attitude that, since it is not on a list of deadly sins, it is not too serious. Hence, you do not feel the need to seek God's forgiveness right away. A week passes and you have completely forgotten about what you had done. You never sought God's forgiveness; as a result, you did not receive it, either. We should go to Confession when we sin – at the very least, we should ask God to forgive us daily in our personal prayers. We should not see Confession as a time to confess only those sins which may be found on a list.

Though not part of the dogma of the Orthodox Church the mortal–venial distinction is assumed by some Orthodox authors and saints as a theologoumenon. For example, Saint Ignatius Brianchaninov (1807–1867), who wrote primarily for monks, says in his book A Word on Death, in a chapter entitled "Mortal sin":

It has been said earlier that mortal sin of an Orthodox Christian, not being cured by repentance, submits him to eternal suffering; it has also been said that the unbelievers, Muslims, and other non-orthodox, even here are the possession of hell, and are deprived of any hope of salvation, being deprived of Christ, the only means of salvation. Mortal sins for Christians are the next: heresy, schism, blasphemy, apostasy, witchery, despair, suicide, fornication, adultery, unnatural carnal sins,^[b] incest, drunkenness, sacrilege, murder, theft, robbery, and every cruel and brutal injury. Only one of these sins – suicide – cannot be healed by repentance, and every one of them slays the soul and makes the soul incapable of eternal bliss, until he/she cleans himself/herself with due repentance. If a man falls but once in any of these sins, he dies by soul: For whosoever shall keep the whole law, and yet offend in one, he is guilty of all. For he that said, Do not commit adultery, said also, Do not kill. Now if thou commit no adultery, yet if thou kill, thou art become a transgressor of the law. (James 2:10,11)

Similarly, the Exomologetarion of Nicodemus the Hagiorite (1749–1809) distinguishes seven classes of sin:^[105]: 83

1. Pardonable
2. Near the pardonable
3. Non-mortal
4. Near the non-mortal
5. Between the mortal and the non-mortal
6. Near the mortal
7. Mortal

Nicodemus gives the following example for the seven classes of sin. "The initial movement of anger is pardonable; near to the pardonable is for someone to say harsh words and get hot-tempered. A non-mortal sin is to swear; near the non-mortal is for someone to strike with the hand. Between the non-mortal and the mortal is to strike with a small stick; near the mortal is to strike with a large stick, or with a knife, but not in the area of the head. A mortal sin is to murder. A similar pattern applies to the other sins. Wherefore, those sins nearer to the pardonable end are penanced lighter, while those nearer to the mortal end are more severely penanced."

He also stipulates seven conditions of sin:^[105]: 100

1. Who is the doer of the sin
2. What sin was committed
3. Why was it committed
4. In what manner was it committed
5. At what time/age was it committed
6. Where was it committed
7. How many times was it committed

• Ancestral sin
• Blasphemy against the Holy Ghost
• Blood atonement
• Original sin
• Seven deadly sins
• Sins that cry to heaven
• Jewish views on sin
• Islamic views on sin
• Catholic hamartiology

• Challoner, Richard (1801). "Day 19: On mortal sin." . Think Well On't or, Reflections on the great truths of the Christian religion for every day of the month. T. Haydock.
• Martin Chemnitz, Andrew L. Packer (2020). "Mortal and Venial Sins". Our Savior Lutheran Church, Pagosa Springs. Archived from the original on 12 August 2020.
• Hanna, Edward Joseph (1908). "Contrition" . In Herbermann, Charles (ed.). Catholic Encyclopedia. Vol. 4. New York: Robert Appleton Company.
• Liguori, Alphonus (1882). "Sermon VI.: On the malice of mortal sin" . Sermons for all the Sundays in the year. Dublin.
• O'Neil, Arthur Charles (1912). "Sin" . In Herbermann, Charles (ed.). Catholic Encyclopedia. Vol. 14. New York: Robert Appleton Company.
• The Council of Trent - Session XIV - The fourth under the Supreme Pontiff, Julius III, celebrated on November 25, 1551 - The Most Holy Sacraments Of Penance And Extreme Unction