The Finnish Civil War was a civil war in Finland in 1918 fought for the leadership and control of the country between White Finland and the Finnish Socialist Workers' Republic during the country's transition from a grand duchy ruled by the Russian Empire to a fully independent state. The clashes took place in the context of the national, political, and social turmoil caused by World War I in Europe. The war was fought between the Red Guards, led by a section of the Social Democratic Party, and the White Guards, conducted by the senate and those who opposed socialism with assistance late in the war by the German Imperial Army at the request of the Finnish civil government. The paramilitary Red Guards, which were composed of industrial and agrarian workers, controlled the cities and industrial centres of southern Finland. The paramilitary White Guards, which consisted of land owners and those in the middle and upper classes, controlled rural central and northern Finland, and were led by General C. G. E. Mannerheim.

A civil war is a war between organized groups within the same 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 Latin bellum civile which was used to refer to the various civil wars of the Roman Republic in the 1st century BC.