Katsuren Castle, Ryukyuan castle ruins in Uruma, Japan

Katsuren Castle is a gusuku ruin on a Ryukyuan limestone hill 60 to 100 metres above sea level at the southern base of the Katsuren Peninsula, with the Pacific Ocean on two sides. It comprises the southern castle (Hegusuku), the middle enclosure and the northern castle (Nishigusuku), whose first, second and third baileys step up a slope, the first bailey highest. In the second bailey lie the foundation stones of a building about 17 m wide and 14.5 m deep.

Katsuren Castle was built in the early 14th century by Katsuren Aji, fifth son of King Taisei of the Eiso dynasty. Its last lord, Amawari, seized power from the ninth Aji, Mochitsuke, promoted overseas trade, and was defeated by the royal court in 1458, after which the castle fell into ruins.

Within the first bailey stands an active shrine of the Ryukyuan religion dedicated to Kobazukasa. Near the castle is Hamagawa Gā, where legend says Manandaru, daughter of the seventh lord Hamagawa Aji, washed hair one and a half times her body length. Folklorist Yanagita Kunio argued from the Omoro Sōshi that a Katsuren culture distinct from Urasoe's existed, likening it to Kamakura.

The site is accessible throughout the year with walking paths leading through the ruins. Wearing sturdy shoes is recommended as the terrain is uneven and the limestone hill features steep sections.

Excavations at this location uncovered unexpected artifacts including Chinese porcelain and ancient Roman coins that point to surprising trading contacts. These discoveries reveal that connections from this region extended far beyond East Asia and reached toward distant Mediterranean networks.