is an active volcano located on the border of Akita and Yamagata in the Tà Âhoku region of Japan, and is tall. Because of its (roughly) symmetrical shape and massive size, it is also variously known as , or depending on the location of the viewer. In addition to being one of the 100 Famous Landscapes of Japan, it is also included as one of the 100 famous mountains in Japan, and famous 100 Geographical Features of Japan. It is surrounded by Chà Âkai Quasi-National Park. It is also a National Historic Site of Japan, and is regarded as a sacred mountain by followers of the Shugendà  branch of Shinto which has the shrine Chà Âkaisan à Âmonoimi Shrine there and is popular with hikers.
Mount Chà Âkai is a complex stratovolcano made of two old and new newer volcanoes, composed primarily of basalt or andesite.
Mount Chà Âkai is shared by two municipalities in Akita Prefecture and four municipalities Yamagata Prefecture; however, its peak is located in Yuza, on the Yamagata side of the border. It is therefore the highest peak in Yamagata, and the second highest in the Tà Âhoku region after Mt. Hiuchigatake (altitude 2,356 m). The highest elevation of Mount Chà Âkai within Akita Prefecture has an altitude of 1,775 meters, and thus the mountain is also the highest in Akita Prefecture. From the summit, it is possible to see the Shirakami Mountains and Mount Iwaki to the north, Sado Island to the south and the Pacific Ocean to the east.
On the south side of the mountain is âÂÂShinji Sekkei,â where snow remains in the shape of the kanji for âÂÂheartâ in even in summer, and portions of the summit have perennial snow, and geological evidence of glaciation in the recent past.
Indigenous species of Mount Chà Âkai include the butterfly thistle and butterfly fish.
Mount Chà Âkai is a very active mountain. Known major eruptions occurred:
Mount Chà Âkai has been the object of mountain worship since ancient times. From the Heian period, it gradually became a training ground for Shugendà Â, as an avatar of Yakushi Nyorai. From the south was a pilgrimage path to the summit. In the middle of the Edo period the mountain drew many pilgrims and had 33 chapels at its base., with additional routes to its summit opened in the north. There is also a tradition that the island of Tobishima in the Sea of Japan was originally a part of the summit of Mount Chokai.
is the God of the mountain and worshipped at Chà Âkaisan à Âmonoimi Shrine.
Three ships have been named after Mount Chà Âkai: Chà Âkai, an early steam gunboat, and the cruiser (sunk in 1944), which were both in the Imperial Japanese Navy, and the JDS Chà Âkai, a Kongà  class guided missile destroyer currently in service in the Japan Maritime Self-Defense Force.