The bogeyman (/ˈboʊɡimæn/; also spelled or known as bogyman, bogy, or bogey, and boogeyman in the United States and Canada) is a mythical creature typically used to frighten children into good behavior. Bogeymen have no specific appearances, and conceptions vary drastically by household and culture, but they are most commonly depicted as masculine, androgynous or even feminine monsters that punish children for misbehaviour. The bogeyman, and conceptually similar monsters, can be found in many cultures around the world. Bogeymen may target a specific act or general misbehavior, depending on the purpose of invoking the figure, often on the basis of a warning from an authority figure to a child. The term is sometimes used as a non-specific personification of, or metonym for, terror – and sometimes the Devil.

The word bogeyman, used to describe a monster in English, may have derived from Middle English bugge or bogge, which means 'frightening specter', 'terror', or 'scarecrow'. It relates to boggart, bugbear (from bug, meaning 'goblin' or 'scarecrow' and bear) an imaginary demon in the form of a bear that ate small children. It was also used to mean a general object of dread. The word bugaboo, with a similar pair of meanings, may have arisen as an alteration of bugbear. Bogeyman itself is known from the 15th century, though bogeyman stories are likely to be much older.

The word has equivalents in many European languages as bogle (Scots), púca, pooka or pookha (Irish), pwca, bwga or bwgan (Welsh), bucca (Cornish), buse or busemann (Norwegian), puki (Old Norse), bøhmand or bussemand (Danish), bûzeman (Western Frisian), boeman (Dutch), boeboelaas (Surinamese Dutch), Butzemann (German), Böölimaa (Swiss German), Babay/Babayka, búka (Russian), bauk (Serbian), bubulis (Latvian), baubas (Lithuanian), bobo (babok, bebok) (Polish), buba/gogol (Albanian), bubák (Czech), bubák (Slovak), bebok (Silesian), papão (Portuguese), bampoúlas (Greek), babau (also uomo nero, meaning black man) (Italian), babáj (Ukrainian),^{[citation needed]} baubau (Romanian), papu (Catalan), and mumus (Hungarian).

It is often described as a dark, formless creature with shapeshifting abilities. The bogeyman is known to satiate its appetite by snatching and consuming children. Descriptions of the bogeyman vary across cultures, yet there are often commonalities between them including claws/talons, or sharp teeth. The nature of the creature also varies from culture to culture, although most examples are said to be a kind of spirit, with demons, witches, and other legendary creatures being less common variants. Some are described as having animal features such as horns, hooves, or a bug-like appearance.^{[unreliable source?]}

Because of the myth's global prevalence, it is difficult to find the original source of the legends. The Bogeyman was first referenced for the hobgoblins described in the 16th century England. Many believed that they were made to torment humans, and while some only played simple pranks, others were more foul in nature.^{[unreliable source?]}

Bogeymen, or bogeyman-like beings, are common to the folklore of many cultures, with numerous variations and equivalents.

The Sack Man is a variant of the Bogeyman folklore which, as its name suggests, stuffs children into a sack. It predominantly exists in the culture of Latin American countries, such as Argentina, Uruguay, Chile, Paraguay and Brazil; as well as in Iberian culture (Spain and Portugal), where the variant originated and whence it was brought over to the Americas through colonization.

It is sometimes referred to as el hombre del costal, el hombre de la bolsa, el hombre del saco, or in Portuguese, o homem do saco; all such names meaning either "the sack man" or "the bag man". It may also be known as el viejo del saco (in Spanish) or o velho do saco (in Portuguese), which mean "the old man with the sack". Another Spanish-language variation is el roba-chicos, "the child-stealer".