The Kuromaru (黒丸), or "Black Fortress", was a fortress of the Kanrei Shiba Takatsune located in Echizen Province (present-day Nittazuka, Fukui, Fukui Prefecture) in the Hokuriku region of Japan. It was attacked twice during the Nanboku-chō Wars of the 14th century, during which it was likely both built and destroyed.
The fortress was first attacked in August 1338 by a small force under Nitta Yoshisada, numbering roughly fifty horse, in what would come to be known as the Battle of Fujishima. Hosokawa Akiuji had been ordered by Ashikaga Takauji to aid Shiba Takatsune in the defense, and encountered Nitta's force a short distance from the fortress.