Belphegor (or Baal Peor, Hebrew: בַּעַל-פְּעוֹר baʿal-pəʿōr – “Lord of the Gap”) is, in the Abrahamic religions, a demon associated with one of the seven deadly sins. According to religious tradition, he helps people make discoveries. He seduces people by proposing incredible inventions that will make them rich. According to some demonologists from the 17th century, his powers are strongest in April. The German bishop and witch hunter, Peter Binsfeld (ca. 1540–ca.1600) wrote that Belphegor tempts through laziness. According to Binsfeld's Classification of Demons, Belphegor is the main demon of the deadly sin known as sloth in the Christian tradition. The anonymous author of the Lollard tract The Lanterne of Light, however, believed Belphegor to embody the sin of gluttony rather than sloth.^[1]

Belphegor derives from the Assyrian Baal-Peor, a Baal worshipped at Mount Peor, to whom the Israelites were associated in Shittim (Numbers 25:3) and who was associated with intemperance and orgies. It was worshiped in the form of a phallus. As a demon, he is described in Kabbalistic writings as "the one who quarrels", an enemy of the sixth Sefirot "beauty". In stories where he was invoked, he bestows wealth, power to make discoveries and make fantastic inventions. His role as a demon was to sow dispute between people, and to lead them to evil through the distribution of wealth.

The palindrome prime number 1000000000000066600000000000001 is known as Belphegor's prime, due to the superstitious significance of the numbers it contains. Belphegor's prime number consists of the number 666, surrounded on both sides by thirteen zeros and finally one one.

According to De Plancy's Dictionnaire Infernal, Belfegor was Hell's ambassador to France. As a result, his enemy is St Mary Magdalene, one of the patron saints of France.

The novella Belfagor arcidiavolo by Italian diplomat Niccolò Machiavelli was first published in 1549, and regales how the demon comes to earth to find a mate.

Belphegor figures in Paradise Lost by John Milton, 1667.

According to the 1818 Dictionnaire Infernal by Collin de Plancy, Belphegor was Hell's ambassador to France. The same claim was repeated by Victor Hugo in Toilers of the Sea (1866).

In the grimoire Key of Solomon (translated into English by S.L. Mathers in 1889), Belphegor is listed near the end of the book as an Assyrian idol, now destroyed.

The novella by Machiavelli became the basis for the opera Belfagor by Ottorino Respighi, which premiered at La Scala in Milan in 1923.

• The PZL M-15 Belphegor, a 1970s Polish utility aeroplane, was named after the demon, due to its strange looks, the noise of its jet engine, and its unsuitability for crop dusting, for which it had been specifically designed.
• Belphegor appears as a supporting character during the “Ghostpocalypse” story-arc during the final season of the TV show Supernatural played by Alexander Calvert, the same actor for the character, Jack Kline; during his time on the show, he possesses the corpse of Jack, who was smited by Chuck, donning white sunglasses to hide Jack’s burnt out eye sockets.
• Belphegor is a recurring demon/persona in the Megami Tensei and Persona video game series.
• Belphegor is the youngest and seventh sibling among the seven demon brothers in the otome game Obey Me!. He is always napping and constantly sleepy and the twin brother of Beelzebub.
• Belphegor is a blackened death metal band.
• Belphegor is the Storm Guard of the Varia in the anime and manga series Katekyo Hitman Reborn. He is also known as 'Prince the Ripper'.
• Belphegor is the name one of the heretical gods, more specifically that of yellow luxin and sloth, in the Lightbringer series by Brent Weeks.
• The long-running German dime novel and audio drama series John Sinclair featured Belphégor as a recurring villain. Author Jason Dark depicted Belphégor as an archdemon mainly active in Paris and a close ally of the Grim Reaper.
• Belphegor is a random demon/monster encounter in the Square Enix games Final Fantasy IV and Final Fantasy XVI.
• Belphegor is a young female demon in the series As Miss Beelzebub Likes. One of the main characters, and the love interest of Azazel.
• Belphegor is referenced in the television show Elementary season three episode three.
• Belphegor is referenced in the short story Bulldozer by Laird Barron.
• A Digimon named Belphemon, from the Digimon franchise is a member of the Seven Great Demon Lords and appears in the fifth season Digimon Data Squad.
• Void Stranger contains a number of characters with abbreviated demon names, including Gor, whose full name is Belphegor.
• Belphegor is mentioned by Beelzebub in episode 8, season 1 in Helluva Boss. It is implied that the character identifies as female and rules over the circle of Sloth, the last circle in Hell. It is also implied she has a connection with medication and drugs in Hell from other references in the show. She later makes a full appearance in episode 11, season 2.
• In One Piece, Magellan, the warden of the prison Impel Down, is heavily based on Belphegor; visually, with distinctive devil horns, and thematically, as the character sits on the toilet for ten hours a day to relieve himself of diarrhea instead of doing his prison duties.
• Belphegor is a title of a song by a visual kei band The Gallo.
• In the video game Infernax, Belphegor is the final boss unless the player pursues one of the three golden endings.

• Belphegor's prime