Spontaneous combustion is the ignition of materials stored in bulk. This is due to internal heat buildup caused by oxidation (generally a reaction in which electrons are lost, specifically when oxygen is combined with a substance, or when hydrogen is removed from a compound). Because this oxidation heat cannot be dissipated into the surrounding air, the temperature of the material rises until the material reaches its ignition point and bursts into flame.

A Chinese text written before 290C.E. recognized this phenomenon in a description of the ignition of stored oiled cloth. The first Western acknowledgment of spontaneous combustion was by J. P. F. Duhamel in 1757, when he discussed the gigantic conflagration of a stack of oil-soaked canvas sails drying in the July sun. Before spontaneous combustion was recognized, such events were usually blamed on arsonists.