A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires and wildfires. Although the word has been used to describe certain large fires, the phenomenon's determining characteristic is a fire with its own storm-force winds from every point of the compass. The  Black Saturday bushfires and the Great Peshtigo Fire are possible examples of forest fires with some portion of combustion due to a firestorm. Firestorms can also occur in cities, usually as a deliberate effect of targeted explosives such as occurred as a result of the aerial firebombings of Hamburg, Dresden, and the atomic bombing of Hiroshima.

Firestorm is the name of several fictional superheroes appearing in American comic books published by DC Comics. Ronnie Raymond and Martin Stein debuted as the first incarnation in Firestorm, the Nuclear Man No. 1 (March 1978) and was created by Gerry Conway and Al Milgrom. Ronnie Raymond (by himself as the second incarnation) debuted in Firestorm the Nuclear Man vol. 2 No. 100 (August 1990), and was created by John Ostrander and Tom Mandrake. Jason Rusch (as the third incarnation) debuted in Firestorm vol. 3 No. 1, (July 2004), and was created by Dan Jolley and Chris Cross.