A devil is the mythical personification of evil as it is conceived in various cultures and religious traditions. It is seen as the objectification of a hostile and destructive force. Jeffrey Burton Russell states that the different conceptions of the devil can be summed up as 1) a principle of evil independent from God, 2) an aspect of God, 3) a created being turning evil (a fallen angel) or 4) a symbol of human evil.

Each tradition, culture, and religion with a devil in its mythos offers a different lens on manifestations of evil. The history of these perspectives intertwines with theology, mythology, psychiatry, art, and literature, developing independently within each of the traditions. It occurs historically in many contexts and cultures, and is given many different names—Satan (Judaism), Lucifer (Christianity), Beelzebub (Judeo-Christian), Mephistopheles (German), Iblis (Islam)—and attributes: it is portrayed as blue, black, or red; it is portrayed as having horns on its head, and without horns, and so on.

The Modern English word devil derives from the Middle English devel, from the Old English dēofol, that in turn represents an early Germanic borrowing of the Latin diabolus. This in turn was borrowed from the Greek διάβολος diábolos, "slanderer", from διαβάλλειν diabállein, "to slander" from διά diá, "across, through" and βάλλειν bállein, "to hurl", probably akin to the Sanskrit gurate, "he lifts up".

In his book The Devil: Perceptions of Evil from Antiquity to Primitive Christianity, Jeffrey Burton Russell discusses various meanings and difficulties that are encountered when using the term devil. He does not claim to define the word in a general sense, but he describes the limited use that he intends for the word in his book—limited in order to "minimize this difficulty" and "for the sake of clarity". In this book Russell uses the word devil as "the personification of evil found in a variety of cultures", as opposed to the word Satan, which he reserves specifically for the figure in the Abrahamic religions.

In the Introduction to his book Satan: A Biography, Henry Ansgar Kelly discusses various considerations and meanings that he has encountered in using terms such as devil and Satan, etc. While not offering a general definition, he describes that in his book "whenever diabolos is used as the proper name of Satan", he signals it by using "small caps".

The Oxford English Dictionary has a variety of definitions for the meaning of "devil", supported by a range of citations: "Devil" may refer to Satan, the supreme spirit of evil, or one of Satan's emissaries or demons that populate Hell, or to one of the spirits that possess a demoniac person; "devil" may refer to one of the "malignant deities" feared and worshiped by "heathen people", a demon, a malignant being of superhuman powers; figuratively "devil" may be applied to a wicked person, or playfully to a rogue or rascal, or in empathy often accompanied by the word "poor" to a person—"poor devil".

In the Baháʼí Faith, a malevolent, superhuman entity such as a devil or satan is not believed to exist. However, these terms do appear in the Baháʼí writings, where they are used as metaphors for the lower nature of man. Human beings are seen to have free will, and are thus able to turn towards God and develop spiritual qualities or turn away from God and become immersed in their self-centered desires. Individuals who follow the temptations of the self and do not develop spiritual virtues are often described in the Baháʼí writings with the word satanic. The Baháʼí writings also state that the devil is a metaphor for the "insistent self" or "lower self", which is a self-serving inclination within each individual. Those who follow their lower nature are also described as followers of "the Evil One".

In Christianity, the devil or Satan is a fallen angel who is the primary opponent of God. Some Christians also considered the Roman and Greek deities to be devils.

Christianity describes Satan as a fallen angel who terrorizes the world through evil, is opposed to truth, and shall be condemned, together with the fallen angels who follow him, to eternal fire at the Last Judgment.

In mainstream Christianity, the devil is usually referred to as Satan. This is because Christian beliefs in Satan are inspired directly by the dominant view of Second Temple Judaism (recorded in the Enochian books), as expressed/practiced by Jesus, and with some minor variations. Some modern Christians consider the devil to be an angel who, along with one-third of the angelic host (the demons), rebelled against God and has consequently been condemned to the Lake of Fire. He is described as hating all humanity (or more accurately all creation), opposing God, spreading lies and wreaking havoc on their souls.

In the Bible, the devil is identified as "the dragon" and "the old serpent" in the Book of Revelation, as "the prince of this world" in the Gospel of John; "the spirit that now worketh in the children of disobedience" in the Epistle to the Ephesians; and "the god of this world" in 2 Corinthians 4:4. He is also identified as the tempter of the Gospels. Satan is traditionally identified as the serpent who convinced Eve to eat the forbidden fruit; thus, Satan has often been depicted as a serpent.

Beelzebub is originally the name of a Philistine god (more specifically a certain type of Baal, from Ba‘al Zebûb, lit. "Lord of Flies") but is also used in the New Testament as a synonym for the devil. A corrupted version, "Belzeboub", appears in The Divine Comedy (Inferno XXXIV).

In other, non-mainstream, Christian beliefs (e.g. the beliefs of the Christadelphians) the word "satan" in the Bible is not regarded as referring to a supernatural, personal being but to any 'adversary' and figuratively refers to human sin and temptation.

In the Book of Wisdom, the devil is represented as the one who brought death into the world. The Second Book of Enoch contains references to a Watcher called Satanael, describing him as the prince of the Grigori who was cast out of heaven and an evil spirit who knew the difference between what was "righteous" and "sinful".

In the Book of Jubilees, Satan rules over a host of angels. Mastema, who induced God to test Abraham through the sacrifice of Isaac, is identical with Satan in both name and nature. The Book of Enoch contains references to Sathariel, thought also to be Sataniel and Satan'el. The similar spellings mirror that of his angelic brethren Michael, Raphael, Uriel, and Gabriel, previous to his expulsion from Heaven.

Gnostic and Gnostic-influenced religions postulate the idea that the material world is inherently evil. The One true God is remote, beyond the material universe; therefore, this universe must be governed by an inferior imposter deity. This deity was identified with the deity of the Old Testament by some sects, such as the Sethians and the Marcions. Tertullian accuses Marcion of Sinope, that he

[held that] the Old Testament was a scandal to the faithful … and … accounted for it by postulating [that Jehovah was] a secondary deity, a demiurgus, who was god, in a sense, but not the supreme God; he was just, rigidly just, he had his good qualities, but he was not the good god, who was Father of Our Lord Jesus Christ.

John Arendzen (1909) in the Catholic Encyclopedia (1913) mentions that Eusebius accused Apelles, the 2nd-century AD Gnostic, of considering the Inspirer of Old Testament prophecies to be not a god, but an evil angel. These writings commonly refer to the Creator of the material world as "a demiurgus" to distinguish him from the One true God. Some texts, such as the Apocryphon of John and On the Origin of the World, not only demonized the Creator God but also called him by the name of the devil in some Jewish writings, Samael.

In the 12th century in Europe the Cathars, who were rooted in Gnosticism, dealt with the problem of evil, and developed ideas of dualism and demonology. The Cathars were seen as a serious potential challenge to the Catholic church of the time. The Cathars split into two camps. The first is absolute dualism, which held that evil was completely separate from the good God, and that God and the devil each had power. The second camp is mitigated dualism, which considers Lucifer to be a son of God and a brother to Christ. To explain this, they used the parable of the prodigal son, with Christ as the good son, and Lucifer as the son that strayed into evilness. The Catholic Church responded to dualism in AD 1215 in the Fourth Lateran Council, saying that God created everything from nothing, and the devil was good when he was created, but he made himself bad by his own free will. In the Gospel of the Secret Supper, Lucifer, just as in prior Gnostic systems, appears as a demiurge, who created the material world.

In Islam, the principle of evil is expressed by two terms referring to the same entity: Shaitan (meaning astray, distant or devil) and Iblis. Iblis is the proper name of the devil representing the characteristics of evil. Iblis is mentioned in the Quranic narrative about the creation of humanity. When God created Adam, he ordered the angels to prostrate themselves before him. Out of pride, Iblis refused and claimed to be superior to Adam. Therefore, pride but also envy became a sign of "unbelief" in Islam. Thereafter, Iblis was condemned to Hell, but God granted him a request to lead humanity astray, knowing the righteous would resist Iblis' attempts to misguide them. In Islam, both good and evil are ultimately created by God. But since God's will is good, the evil in the world must be part of God's plan. Actually, God allowed the devil to seduce humanity. Evil and suffering are regarded as a test or a chance to prove confidence in God. Some philosophers and mystics emphasized Iblis himself as a role model of confidence in God. Because God ordered the angels to prostrate themselves, Iblis was forced to choose between God's command and God's will (not to praise someone other than God). He successfully passed the test, yet his disobedience caused his punishment and therefore suffering. However, he stays patient and is rewarded in the end.

Muslims hold that the pre-Islamic jinn, tutelary deities, became subject under Islam to the judgment of God, and that those who did not submit to the law of God are devils.

Although Iblis is often compared to the devil in Christian theology, Islam rejects the idea that Satan is an opponent of God and the implied struggle between God and the devil. Iblis might either be regarded as the most monotheistic or the greatest sinner, but remains only a creature of God. Iblis did not become an unbeliever due to his disobedience, but because of attributing injustice to God; that is, by asserting that the command to prostrate himself before Adam was inappropriate. There is no reference to angelic revolt in the Quran and no mention of Iblis trying to take God's throne, and Iblis's sin could be forgiven at any time by God. According to the Quran, Iblis's disobedience was due to his disdain for humanity, a narrative already occurring in early New Testament apocrypha.

As in Christianity, Iblis was once a pious creature of God but later cast out of Heaven due to his pride. However, to maintain God's absolute sovereignty, Islam matches the line taken by Irenaeus instead of the later Christian consensus that the devil did not rebel against God but against humanity. Further, although Iblis is generally regarded as a real bodily entity, he plays a less significant role as the personification of evil than in Christianity. Iblis is merely a tempter, notable for inciting humans into sin by whispering into humans minds (waswās), akin to the Jewish idea of the devil as yetzer hara.

On the other hand, Shaitan refers unilaterally to forces of evil, including the devil Iblis who causes mischief. Shaitan is also linked to humans' psychological nature, appearing in dreams, causing anger, or interrupting the mental preparation for prayer. Furthermore, the term Shaitan also refers to beings who follow the evil suggestions of Iblis. Also, the principle of shaitan is in many ways a symbol of spiritual impurity, representing humans' own deficits, in contrast to a "true Muslim", who is free from anger, lust and other devilish desires.

In Muslim culture, devils are believed to be hermaphrodite creatures created from hell-fire, with one male and one female thigh, and able to procreate without a mate. It is generally believed that devils can harm the souls of humans through their whisperings. While whisperings tempt humans to sin, the devils might enter the hearth (qalb) of an individual. If the devils take over the soul of a person, this would render them aggressive or insane. In extreme cases, the alterings of the soul are believed to have effect on the body, matching its spiritual qualities.

In contrast to Occidental philosophy, the Sufi idea of seeing "Many as One" and considering the creation in its essence as the Absolute, leads to the idea of the dissolution of any dualism between the ego substance and the "external" substantial objects. The rebellion against God, mentioned in the Quran, takes place on the level of the psyche that must be trained and disciplined for its union with the spirit that is pure. Since psyche drives the body, flesh is not the obstacle to humans but rather an unawareness that allows the impulsive forces to cause rebellion against God on the level of the psyche. Yet it is not a dualism between body, psyche and spirit, since the spirit embraces both psyche and corporeal aspects of humanity. Since the world is held to be the mirror in which God's attributes are reflected, participation in worldly affairs is not necessarily seen as opposed to God. The devil activates the selfish desires of the psyche, leading the human astray from the Divine. Thus, it is the I that is regarded as evil, and both Iblis and Pharao are present as symbols for uttering "I" in ones own behavior. Therefore, it is recommended to use the term I as little as possible. It is only God who has the right to say "I", since it is only God who is self-subsistent. Uttering "I" is therefore a way to compare oneself to God, regarded as shirk.

Many Salafi strands emphasize a dualistic worldview between believers and unbelievers, The unbelievers are considered to be under the domain of the Devil and are the enemies of the faithful. The former are credited with tempting the latter to sin and away from God's path. The Devil will ultimately be defeated by the power of God, but remains until then a serious threat for the believer.

The notion of a substantial reality of evil (or a form of dualism between God and the Devil) has no precedence in the Quran or earlier Muslim traditions. Neither in the writings of ibn Sina, Ghazali, nor ibn Taimiyya, has evil any positive existence, but is described as the absense of good. Accordingly, infidelity among humans, civilizations, and empires are not described evil or devilish in Classical Islamic sources. This is in stark contrast to Islamists, such as Osama bin Laden, who justifies his violance against the infidels by contrary assertions.

While in classical hadiths, devils (shayāṭīn) and jinn are responsible for ritual impurity, many Salafis substitute local demons by an omnipresent threat through the Devil himself. Only through remembrance of God and ritual purity, the devil can be kept away. As such, the Devil becomes an increasinly powerful entity who is believed to interfer with both personal and political life. For example, many Salafis blame the Devil for Western emancipation.

Yahweh, the god in pre-exilic Judaism, created both good and evil, as stated in Isaiah 45:7: "I form the light, and create darkness: I make peace, and create evil: I the Lord do all these things." The devil does not exist in Jewish scriptures. However, the influence of Zoroastrianism during the Achaemenid Empire introduced evil as a separate principle into the Jewish belief system, which gradually externalized the opposition until the Hebrew term satan developed into a specific type of supernatural entity, changing the monistic view of Judaism into a dualistic one. Later, Rabbinic Judaism rejected the Enochian books (written during the Second Temple period under Persian influence), which depicted the devil as an independent force of evil besides God. After the apocalyptic period, references to Satan in the Tanakh are thought to be allegorical.

In Mandaean mythology, Ruha fell apart from the World of Light and became the queen of the World of Darkness, also referred to as Sheol. She is considered evil and a liar, sorcerer and seductress.She gives birth to Ur, also referred to as Leviathan. He is portrayed as a large, ferocious dragon or snake and is considered the king of the World of Darkness. Together they rule the underworld and create the seven planets and twelve zodiac constellations. Also found in the underworld is Krun, the greatest of the five Mandaean Lords of the underworld. He dwells in the lowest depths of creation and his epithet is the 'mountain of flesh'. Prominent infernal beings found in the World of Darkness include lilith, nalai (vampire), niuli (hobgoblin), latabi (devil), gadalta (ghost), satani (Satan) and various other demons and evil spirits.

In Manichaeism, God and the devil are two unrelated principles. God created good and inhabits the realm of light, while the devil (also called the prince of darkness) created evil and inhabits the kingdom of darkness. The contemporary world came into existence, when the kingdom of darkness assaulted the kingdom of light and mingled with the spiritual world. At the end, the devil and his followers will be sealed forever and the kingdom of light and the kingdom of darkness will continue to co-exist eternally, never to commingle again.

Hegemonius (4th century CE) accuses that the Persian prophet Mani, founder of the Manichaean sect in the 3rd century CE, identified Jehovah as "the devil god which created the world" and said that "he who spoke with Moses, the Jews, and the priests … is the [Prince] of Darkness, … not the god of truth."

Among the Tengristic myths of central Asia, Erlik refers to a devil-like figure as the ruler of Tamag (Hell), who was also the first human. According to one narrative, Erlik and God swam together over the primordial waters. When God was about to create the Earth, he sent Erlik to dive into the waters and collect some mud. Erlik hid some inside his mouth to later create his own world. But when God commanded the Earth to expand, Erlik got troubled by the mud in his mouth. God aided Erlik to spit it out. The mud carried by Erlik gave place to the unpleasant areas of the world. Because of his sin, he was assigned to evil. In another variant, the creator-god is identified with Ulgen. Again, Erlik appears to be the first human. He desired to create a human just as Ulgen did, thereupon Ulgen reacted by punishing Erlik, casting him into the Underworld where he becomes its ruler.

According to Tengrism, there is no death, meaning that, when life comes to an end, it is merely a transition into the invisible world. As the ruler of Hell, Erlik enslaves the souls, who are damned to Hell. Further, he lurks on the souls of those humans living on Earth by causing death, disease and illnesses. At the time of birth, Erlik sends a Kormos to seize the soul of the newborn, following him for the rest of his life in an attempt to seize his soul by hampering, misguiding, and injuring him. When Erlik succeeds in destroying a human's body, the Kormos sent by Erlik will try take him down into the Underworld. However a good soul will be brought to Paradise by a Yayutshi sent by Ulgen. Some shamans also made sacrifices to Erlik, for gaining a higher rank in the Underworld, if they should be damned to Hell.

According to Yazidism there is no entity that represents evil in opposition to God; such dualism is rejected by Yazidis, and evil is regarded as nonexistent. Yazidis adhere to strict monism and are prohibited from uttering the word "devil" and from speaking of anything related to Hell.

Zoroastrianism probably introduced the first idea of the devil; a principle of evil independently existing apart from God. In Zoroastrianism, good and evil derive from two ultimately opposed forces. The force of good is called Ahura Mazda and the "destructive spirit" in the Avestan language is called Angra Mainyu. The Middle Persian equivalent is Ahriman. They are in eternal struggle and neither is all-powerful, especially Angra Mainyu is limited to space and time: in the end of time, he will be finally defeated. While Ahura Mazda creates what is good, Angra Mainyu is responsible for every evil and suffering in the world, such as toads and scorpions. Iranian Zoroastrians also considered the Daeva as devil creature, because of this in the Shahnameh, it is mentioned as both Ahriman Div (Persian: اهریمن دیو, romanized: Ahriman Div) as a devil.

A non-published manuscript of Spinoza's Ethics contained a chapter (Chapter XXI) on the devil, where Spinoza examined whether the devil may exist or not. He defines the devil as an entity which is contrary to God. However, if the devil is the opposite of God, the devil would consist of Nothingness, which does not exist.

In a paper called On Devils, he writes that we can a priori find out that such a thing cannot exist. Because the duration of a thing results in its degree of perfection, and the more essence a thing possess the more lasting it is, and since the devil has no perfection at all, it is impossible for the devil to be an existing thing. Evil or immoral behaviour in humans, such as anger, hate, envy, and all things for which the devil is blamed for could be explained without the proposal of a devil. Thus, the devil does not have any explanatory power and should be dismissed (Occam's razor).

Regarding evil through free choice, Spinoza asks how it can be that Adam would have chosen sin over his own well-being. Theology traditionally responds to this by asserting it is the devil who tempts humans into sin, but who would have tempted the devil? According to Spinoza, a rational being, such as the devil must have been, could not choose his own damnation. The devil must have known his sin would lead to doom, thus the devil was not knowing, or the devil did not know his sin will lead to doom, thus the devil would not have been a rational being. Spinoza deducts a strict determinism in which moral agency as a free choice, cannot exist.

In Religion Within the Limits of Reason Alone, Immanuel Kant uses the devil as the personification of maximum moral reprehensibility. Deviating from the common Christian idea, Kant does not locate the morally reprehensible in sensual urges. Since evil has to be intelligible, only when the sensual is consciously placed above the moral obligation can something be regarded as morally evil. Thus, to be evil, the devil must be able to comprehend morality but consciously reject it, and, as a spiritual being (Geistwesen), having no relation to any form of sensual pleasure. It is necessarily required for the devil to be a spiritual being because if the devil were also a sensual being, it would be possible that the devil does evil to satisfy lower sensual desires, and does not act from the mind alone. The devil acts against morals, not to satisfy sensual lust, but solely for the sake of evil. As such, the devil is unselfish, for he does not benefit from his evil deeds.

However, Kant denies that a human being could ever be completely devilish. Kant admits that there are devilish vices (ingratitude, envy, and malicious joy), i.e., vices that do not bring any personal advantage, but a person can never be completely a devil. In his Lecture on Moral Philosophy (1774/75) Kant gives an example of a tulip seller who was in possession of a rare tulip, but when he learned that another seller had the same tulip, he bought it from him and then destroyed it instead of keeping it for himself. If he had acted according to his sensual urges, the seller would have kept the tulip for himself to make a profit, but not have destroyed it. Nevertheless, the destruction of the tulip cannot be completely absolved from sensual impulses, since a sensual joy or relief still accompanies the destruction of the tulip and therefore cannot be thought of solely as a violation of morality.

Kant further argues that a (spiritual) devil would be a contradiction. If the devil would be defined by doing evil, the devil had no free choice in the first place. But if the devil had no free-choice, the devil could not have been held accountable for his actions, since he had no free will but was only following his nature.

Honorifics or styles of address used to indicate devil-figures.

Opinion polls show that belief in the devil in Western countries is more common in the United States ...

Belief in the devil in 1982

Country	U.S.	U.K.	France
Percentage	~60	21	17

where it is more common among the religious, regular church goers, political conservatives, and the older and less well educated, ... but has declined in recent decades.

Belief in the devil in the U.S.

Year surveyed	2001	2004	2000	2016	2023
Percentage believing	68	70	70	61	58

• Deal with the Devil
• Devil in popular culture
• Hades, Underworld
• Krampus, in the Tyrolean area also Tuifl
• Non-physical entity
• Theistic Satanism

• The dictionary definition of Devil at Wiktionary
• Media related to Devils at Wikimedia Commons

• Kent, William Henry (1908). "Devil" . Catholic Encyclopedia. Vol. 4.
• Garvie, Alfred Ernest (1911). "Devil" . Encyclopædia Britannica. Vol. 8 (11th ed.). pp. 121–123.
• Entry from the New Advent Catholic Encyclopedia
• Can you sell your soul to the Devil? A Jewish view on the Devil