Nanao Castle is a 15th century castle located in Nanao City, in Ishikawa Prefecture, Japan.
The Hatekeyama clan constructed Nanao Castle around 1400, and in its heyday, it was one of the most important mountaintop fortifications in Japan. After a long siege in 1577, the castle fell to Uesugi Kenshin. The battle caused an escalation of hostilities between Oda Nobunaga and the Uesugi clan, with the Uesugi eventually defeated. Following this, Maeda Toshiie gained the area for his clan, constructing a new castle in Nanao City itself, at Komaruyama.
The castle is now only ruins, with some stone ramparts, baileys. A museum is on site.
Coordinates: 37°00′32″N 136°59′03″E / 37.0089°N 136.9841°E