A civil war is a war between organized groups within the same state or country, or, less commonly, between two countries created from a formerly united state. The aim of one side may be to take control of the country or a region, to achieve independence for a region or to change government policies. The term is a calque of the Latin which was used to refer to the various civil wars of the Roman Republic in the 1st century BC.

A civil war is an armed conflict within a nation.