Zakimi-jo Castle is a gusuku in Yomitan, Okinawa Prefecture, Japan. It is in ruins, but the walls and foundations have been restored. Built between 1416 and 1422 by the renowned Ryukyuan militarist Gosamaru, Zakimi Castle oversaw the northern portion of the Okinawan mainland. The gusuku fortress has two inner courts, each with an arched gate. This is Okinawa's first stone arch gate featuring the unique keystone masonry of the Ryukyus.
Before and during World War II, the castle was used as a gun emplacement by the Japanese, and after the war it was used as a radar station by the US forces. Some of the walls were destroyed in order to install the radar equipment, but they have since been restored.
Zakimi Castle and Okinawa's other castles were named a World Heritage Site by UNESCO in November 2000.