Mount Zaō (蔵王山, Zaō-san) is a complex volcano on the border between Yamagata Prefecture and Miyagi Prefecture in Japan. It consists of a cluster of stratovolcanoes and is the most active volcano in northern Honshu. The central volcano of the group includes several lava domes and a tuff cone, Goshiki-dake, which contains a crater lake named Okama. Also known as the "Five Color Pond" (五色沼, goshiki numa) because it changes color depending on the weather, it lies in a crater formed by a volcanic eruption in the 1720s.