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.