Georgios Siantos (nicknames: Geros "Old man", Theios "Uncle"; Greek: Γεώργιος "Γιώργης" Σιάντος; 1890 – 20 May 1947) was a prominent figure of the Communist Party of Greece (Greek: Κομμουνιστικό Κόμμα Ελλάδας, romanized: Kommunistiko Komma Elladas, KKE) who served as acting general secretary of the party, and as a leader of the National Liberation Front (EAM)/Greek People's Liberation Army (ELAS) Resistance movement during the German occupation of Greece in World War II.