In Japanese Buddhism, Gaki (餓鬼, "hungry ghosts") are the spirits of jealous or greedy people who, as punishment for their mortal vices, have been cursed with an insatiable hunger for a particular substance or object. Traditionally, this is something repugnant or humiliating, such as human corpses or feces, though in more recent legends, it may be virtually anything, no matter how bizarre.

Gaki are often depicted in Japanese art (particularly that from the Heian period) as emaciated human beings with bulging stomachs and inhumanly small mouths and throats. They are frequently shown licking up spilled water in temples or accompanied by demons representing their personal agony. Alternately, they may be shown as balls of smoke or fire.

Gaki are generally little more than nuisances to mortals unless their longing is directed toward something vital, such as blood. However, in some traditions, gaki try to prevent others from satisfying their own desires by means of magic, illusions, or disguises. They can also turn invisible or change their faces to frighten mortals.

Generally, however, gaki are seen as souls to be pitied. Thus, in some zen monasteries, monks leave offerings of food, money, or flowers to them before meals, and since 657, some Japanese Buddhists have observed a special day in mid-August to remember the gaki. Through such offerings and remembrances (segaki), it is believed that the hungry ghosts may be released from their eternal torment.

See also: jikininki