Mount Hongū, Mountain summit in Aichi Prefecture, Japan.

Mount Hongū reaches 789 meters at the border where Toyokawa, Okazaki, and Shinshiro meet in Aichi Prefecture. The wooded slopes contain established hiking trails that lead to the summit and viewpoints overlooking the surrounding region.

Mount Hongū's summit shrine, the Okumiya of Toga Shrine, is the okumiya of the ichinomiya of Mikawa Province, and the mountain has long been a target of worship for people of eastern Mikawa. The summit holds a first-order triangulation point named "Sanhongūzan". The Hongū Skyline road, which reaches near the summit, became toll-free on 1 February 2006.

At the summit stands the Okumiya, the inner sanctuary of Toga Shrine, the ichinomiya of Mikawa Province. People from the eastern Mikawa region have long venerated the mountain as a object of faith, and the Okumiya is reached by climbing a stone stairway where, on clear days, Mount Fuji can be seen partway up.

Trails are open year-round with parking at the base and rest areas along main routes. Wear sturdy hiking shoes and bring water, especially if spending several hours on the mountain.

A first-order triangulation point named "Sanhongūyama" sits at the summit, alongside a dense cluster of antennas of the Toyohashi relay station. On clear days the summit offers a faint view of Mikawa Bay, and a spot partway up the stone steps to the Okumiya reveals Mount Fuji.