Mount Neishi (根石岳, Neishi-dake) is a 2,603m mountain on the border of Chino and Koumi of Nagano in Japan.

This mountain belongs to Northern Yatsugatake Volcanic Group.

This mountain is a part of the Yatsugatake-Chūshin Kōgen Quasi-National Park.

Mount Higashi Tengu (東天狗岳), 2,603 m (8,540 ft), lies to the north, along the main traverse route of the Yatsugatake Mountain Range, and Mount Nishi Tengu, 2,646 m (8,681 ft), is to the northwest.

[1] The main traverse route of the Yatsugatake Mountain Range passes through the summit of Mount Neishi.