Athanasios Klaras, better known by the nom de guerre Aris Velouchiotis, was a Greek journalist, politician, member of the Communist Party of Greece, the most prominent leader and chief instigator of the Greek People's Liberation Army (ELAS) and the military branch of the National Liberation Front (EAM), which was the major resistance organization in occupied Greece from 1942 to 1945.

The Greek People's Liberation Army was the military arm of the left-wing National Liberation Front (EAM) during the period of the Greek resistance until February 1945, when, following the Dekemvriana clashes and the Varkiza Agreement, it was disarmed and disbanded. ELAS was the largest and most significant of the military organizations of the Greek resistance.