Total war is a war in which a belligerent engages in the complete mobilization of fully available resources and population.

In the mid-19th century, "total war" was identified by scholars as a separate class of warfare. In a total war, there is less differentiation between combatants and civilians than in other conflicts, and sometimes no such differentiation at all, as nearly every human resource, civilians and soldiers alike, can be considered to be part of the belligerent effort.

The phrase can be traced back to the 1936 publication of General Ludendorff’s World War I memoir Der Totale Krieg ("The Total War"). The concept is extended by some authors back as far as Clausewitz’s classic work On War as "absoluter Krieg" (however, the relevant passages have been interpreted in diverging ways by different authors), and to the French "guerre à outrance" during the Franco-Prussian War.

USAF General Curtis LeMay updated the concept for the nuclear age. In 1949, he was first to propose that a total war in the nuclear age would consist of delivering the entire nuclear arsenal in a single overwhelming blow, going as far as "killing a nation".