Petrification was a malign magical state in which a living creature was rendered immobile and unresponsive as if it had been turned to stone. It was a phenomenon of the most advanced Dark Magic, affecting beasts, beings, and even spirits such as ghosts. Petrification could be inflicted by the statue curse, along with the gazes of the Gorgon and the Basilisk. In the case of the Basilisk, its gaze ordinarily killed living creatures, but when seen indirectly, or by a ghost (who was already dead and couldn't die again), it caused Petrification instead.

During the history of Hogwarts School of Witchcraft and Wizardry, the Chamber of Secrets was opened twice, and in both cases, the Serpent of Slytherin was released and attacked the Muggle-born student body. The first opening in 1943 resulted in the Petrification of three Muggle-born students, and the death of one, Myrtle Warren. The second opening in 1992 led to the Petrification of students Colin Creevey, Justin Finch-Fletchley, Hermione Granger, and Penelope Clearwater, along with the cat Mrs. Norris and the ghost Sir Nicholas de Mimsy-Porpington.

Victims of Petrification were completely paralyzed and unresponsive. It may have taken a careful examination to discern if a victim was Petrified. A Petrified ghost would turn a dark smoky grey and could only be moved using air currents. The antidote to Petrification was the Mandrake Restorative Draught, a highly potent healing potion made from Stewed Mandrakes.

Petrification should not be confused with the Full Body-Bind Curse or the Hardening Charm. The Full Body-Bind Curse was only temporary and could be lifted easily, while the Hardening Charm turned an object into a literal stone. Gilderoy Lockhart once confused the effects of Petrification with those of the Transmogrifian Torture; However, the truth of his claims was extremely dubious.