Spontaneous human combustion (SHC) describes reported cases of the burning

Combustion

Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 of a living human body without an apparent external source of ignition. There have been about 200 cited cases worldwide over a period of around 300 years.

There are also many hypotheses which attempt to explain the various cases of human spontaneous combustion

Spontaneous combustion

Spontaneous combustion is the self-ignition of a mass, for example, a pile of oily rags. Allegedly, humans can also ignite and burn without an obvious cause; this phenomenon is known as spontaneous human combustion....

:

• Paranormal explanations (e.g., a ghost
  Ghost
  In traditional belief and fiction, a ghost is the soul or spirit of a deceased person or animal that can appear, in visible form or other manifestation, to the living. Descriptions of the apparition of ghosts vary widely from an invisible presence to translucent or barely visible wispy shapes, to...
  
   or divine intervention)
• Natural explanations based on an unknown and otherwise unobserved phenomenon (e.g., production of abnormally concentrated gas or raised levels of blood alcohol cause spontaneous ignition)
• Natural explanations that involve an external source of ignition (e.g., the victim dropped a cigarette)

Objections to natural explanations typically refer to the degree of burning of the body with respect to its surroundings.