In the Dune series of science fiction books by Frank Herbert, spice agony is an ordeal, in which an acolyte of the Bene Gesserit takes a massive overdose of the spice melange and confronts her inner self, and the selves of all her female ancestors. She must also "change" the spice (which is a poison at such high doses), turning it into the Water of Life. If she masters the confrontation, she emerges as a Reverend Mother, a Bene Gesserit of terrifying abilities, fully in command of her Other Memories (the collective egos of her female ancestors.)

Only females can survive the spice agony. In the legends of the novel, however, there will be one man born with the ability to change the spice, known as the Kwisatz Haderach. The Bene Gesserit try over many generations through selective breeding to produce such a being. A Kwisatz Haderach is given different abilities than a Reverend Mother. During the Spice Agony, there are two areas of the soul that the acolyte may visit — the part that gives, and the part that takes. Female acolytes can only visit the part that gives, male acolytes may only visit the part that takes. The Kwisatz Haderach can do both. However, until Paul Atreides all men who attempt the spice agony trial die.