The Yugoslav volunteers in the Spanish Civil War, known as Spanish fighters and Yugoslav brigadistas, was a contingent of volunteers from the Kingdom of Yugoslavia that fought for the Republicans during the Spanish Civil War (1936–1939). An estimated 1,664 "Yugoslav brigadistas" fought in the war, out of whom c. 800 were killed in action. According to Spanish statistics, 148 Yugoslav volunteers received the officer rank during the conflict.

The International Brigades were soldiers set up by the Communist International to assist the Popular Front government of the Second Spanish Republic during the Spanish Civil War. The organization existed for two years, from 1936 until 1938. It is estimated that during the entire war, between 40,000 and 59,000 members served in the International Brigades, including some 10,000 who died in combat. Beyond the Spanish Civil War, "International Brigades" is also sometimes used interchangeably with the term foreign legion in reference to military units comprising foreigners who volunteer to fight in the military of another state, often in times of war.