Kururi Castle, Japanese castle in Kimitsu, Japan

Kururi Castle is a Japanese fortification in Kimitsu, Chiba Prefecture, located on top of Mount Kururi overlooking the surrounding countryside. The reconstructed main tower rises three floors with white plastered exterior walls and wooden frameworks typical of defensive structures from the Sengoku period.

Takeda Nobunaga built the first castle in 1456, and his descendants, the Mariyatsu Takeda, held it until the Satomi clan took over. Satomi Yoshitaka made it his base against the Hōjō, who seized it in 1564 but lost it three years later. In 1590 Tokugawa Ieyasu granted the castle to Matsudaira (Ōsuga) Tadamasa, who built the castle town. The Meiji government destroyed the remaining structures in 1872.

The castle is also called Rain Castle (U-jō) after a legend that it rained twenty-one times during its construction, roughly once every three days. It is also known as Mist Descending Castle and Urada Castle. The hilltop springs, including the Male Well, Female Well and Otama Pond, still hold water.

The JR Kururi Line connects to Kururi Station at the base of the mountain, from where local buses or walking paths lead to the castle grounds. The climb up the hill requires some stamina, but the paths are well maintained and offer rest benches along the way.

The present keep is a 1979 concrete reconstruction modelled on Hamamatsu Castle's mock keep. Records and the arrangement of foundation stones indicate the Edo-period keep was a two-storey, two-roofed building, while the replica has three interior floors. Its interior holds panel displays of surviving keeps across Japan and serves mainly as an observation deck.