Fire Manipulation is the ability to generate and control flames to the users will whether through artificial or natural means.
The potency of flames created varies. Genos can create blasts that blow up stone cliff-faces and a large chunk of a mountain’s top, and Orochi's flames are hot enough to melt stone, whilst Enjoe can barely set another human on fire.
The ability to generate fire may be gained through monsterification or by using mechanical incendiary devices. Enjoe and Hellfire Flame are the only humans shown to be able to generate fire without the use of other tools.