Mount Ishigaki is a mountain located in Odawara City, Kanagawa Prefecture 241.6 meters (792 feet) in height. It is located 2.8 kilometers (1.7 miles) to the south-west of Odawara Castle and is famous for being the place where Toyotomi Hideyoshi built his stronghold, the One-Night Castle, in 1590 during the Siege of Odawara. It was designated a historical landmark in 1959.

The mountain was originally known as Mt. Kasagake, but was renamed Ishigaki, or "stone wall" for the castle ramparts after the siege. Hideyoshi's troops started the castle on April 5th and completed it on June 26th, and it was the first all-stone castle built in the Kantou. The summit of Mt. Ishigaki offered an unbroken view of the entire Odawara Castle area.