Giorgos Siantos (1890 - May 20, 1947) was a Greek communist and acting general secretary of the Communist Party of Greece and a leader of the National Liberation Front (EAM) and National Popular Liberation Army (ELAS) during the German occupation.
Siantos was born in Karditsa, Thessaly in 1890. He served in the Greek army as a sergeant during the Balkan Wars but also became involved in the labour movement. In 1939, he was arrested for Communist-related activities and served time in prison in Corfu. He escaped in 1941. During the German occupation of Greece (1941 - 1944), Siantos led the Communist-dominated Greek National Liberation Army. He also served as acting Secretary General of the Communist Party of Greece (KKE) from 1942 until 1945 in the absence of Nikolaos Zachariadis.
Siantos died of heart attack on May 20, 1947, in the private clinic of the prominent Greek communist doctor, Petros Kokkalis.