An ogre (feminine: ogress) is a large, mean and hideous humanoid monster. Ogres are often depicted in fairy tales and folklore as feeding on human beings, and have appeared in many classic works of literature. In art, ogres are often depicted with a large head, abundant hair and beard, a huge belly, and a strong body. The term is often applied in a metaphorical sense to disgusting persons who exploit, brutalize or devour their victims.

The term "ogre" can also mean a feared, over authoritative, and abusive person.

The word ogre is of French derivation, and was originally believed to have been coined by either Charles Perrault (1628-1703) or Marie-Catherine Jumelle de Berneville, Comtesse d' Aulnoy (1650-1705), both of whom were French authors. Other sources say that the name is derived from the word Hongrois, which means Hungarian. Nowadays, the word is thought to have been actually inspired by the works of Italian author Giambattista Basile (1575-1632), who used the Neapolitan word uerco, in standard Italian orco. This word is documented in earlier Italian works (Fazio degli Uberti, XIV cent.; Luigi Pulci, XV; Ludovico Ariosto, XV-XVI) and has even older cognates with the Latin orcus and the Old English orcnēas found in Beowulf lines 112-113, which inspired J.R.R. Tolkien's Orc. All these words may derive from a shared Indo-European mythological concept (as Tolkien himself speculated).

The first appearance of the word ogre in Perrault's work occurred in his Histoires ou Contes du temps Passé (1697). It later appeared in several of his other fairy tales, many of which were based on the Neapolitan tales of Basile. The first example of a female ogre being referred to as an ogress is found in his version of Sleeping Beauty, where it is spelled ogresse.. The Comtesse d' Aulnoy first employed the word ogre in her story L'Orangier et l' Abeille (1698), and was the first to use the word ogree to refer to the creature's offspring.