The Viannos massacres (Greek: Ολοκαύτωμα της Βιάννου) refers to a mass extermination campaign launched by Nazi forces against the civilian residents of around 20 villages located in the areas of east Viannos and west Ierapetra provinces on the Greek island of Crete during World War II. The killings, with a death toll in excess of 500, were carried out on 14–16 September 1943 by Wehrmacht units. They were accompanied by the burning of most villages, and the looting and destruction of harvests. The massive loss of life amounted to one of the deadliest massacres during the Axis occupation of Greece. It was ordered by Generalleutnant Friedrich-Wilhelm Müller, in retaliation for the support and involvement of the local population in the Cretan resistance.