The Czechoslovak Legion (Československé legie in Czech, Československé légie in Slovak) or Czech legion were volunteer armed forces composed predominantly of Czechs with a small number of Slovaks (approximately 8 percent) fighting together with the Entente powers during World War I. The name "Czechoslovak" originated after the war. Their goal was to win the Allies' support for the independence of Bohemia and Moravia from the Austrian Empire and of Slovak territories from the Kingdom of Hungary, which were then part of the Austro-Hungarian Empire. With the help of émigré intellectuals and politicians such as Tomáš Garrigue Masaryk and Milan Rastislav Štefánik, they grew into a force of tens of thousands.
In Russia, they took part in several battles of the war, including the Zborov and Bakhmach against the Central Powers, and were heavily involved in the Russian Civil War fighting Bolsheviks, at times controlling the entire Trans-Siberian railway and several major cities in Siberia.
After three years of existence as a small unit in the Imperial Russian Army, the Legion in Russia was established in 1917, with other troops fighting in France since the beginning of the war as the "Nazdar" company, and similar units later emerging in Italy and Serbia. Originally an all-volunteer force, these formations were later strengthened by Czech and Slovak prisoners of war or deserters from the Austro-Hungarian Army. The majority of the legionaries were Czechs, with Slovaks making up 7.4% of the force in Russia, 3% in Italy and 16% in France.