Mount Gaki, Mountain summit in Ōmachi, Japan.

Mount Gaki is a 2,647 m granite peak of the Hida Range (Northern Japan Alps) entirely within Nagano Prefecture and Chūbu-Sangaku National Park. A third-order triangulation point stands on the summit, where a dwarf-pine zone gives way to gravel holding colonies of the alpine plant komakusa. About 100 m south of and just below the summit sits the old Gaki-dake mountain hut.

The mountain is listed among Japan's 200 Famous Mountains. Its summit holds a third-order triangulation point. The Gaki-dake hut just below the top was long run by the Fukuhata family; after Tokushige Fukuhata fell to his death in June 1973, management passed to Sōemon Itō. The hut gives out a Gaki charm stamp, and its badge shows a serow.

The name may come from "gake-dake" (cliff peak), after the rock wall seen from Azumino, or from gaki, the hungry ghosts of Buddhist lore; Ōmachi keeps famine legends, and the Kake hot spring near the foot is said to have been found during a famine in the Keichō era (1596–1615) by people gathering kuzu root for food.

Hiking is possible from late spring through early fall, with different trailheads offering access from the surrounding area. Proper equipment and attention to weather changes are important as conditions can shift quickly at this elevation.

The summit sits just above the forest limit, where a band of dwarf pine gives way to gravel holding a colony of Komakusa, the alpine flower Dicentra peregrina. About 100 m south of and just below the top stands Gaki-dake Lodge, a traditional mountain hut with 70 places and space for five tents.