Askio is a mountain range in the northwestern part of the Kozani and the eastern part of the Kastoria regional units in northern Greece. The elevation of its highest peak, Siniatsiko, is . There are forests in the northern part. It stretches from the village Kleisoura in the northwest to Xirolimni in the southeast, over a length of about . The nearest mountains are the Verno to the northwest, the Vourinos to the south and the Vermio to the northeast. It is drained by tributaries of the Aliakmonas to the west and south, and towards the Lake Vegoritida to the northeast.