Akutagawayama Castle, Castle ruins on Mount Miyoshi in Takatsuki, Japan

Akutagawayama Castle is a mountain castle ruin on Mount Miyoshi in Takatsuki, rising 182.6 meters and enclosed on three sides by the Akutagawa River. It consists of three bailey groups: the eastern group with earthen bridge and vertical embankments, the central group with an outwork and a rare stone-lined entrance, and the western group containing the main bailey at the summit.

Hosokawa Takakuni built the castle between 1515 and 1516; the first record of it appears in a January 1516 linked-verse gathering at the 'new Akutagawa Castle.' It passed through the Nose, Hosokawa Harumoto and Miyoshi Nagayoshi, becoming the Miyoshi main line's base. In 1568 Oda Nobunaga's forces burned its foothills, and it was abandoned around 1573 after the Takayama took Takatsuki Castle.

The castle's name is written 芥川山城, but the designation as a national historic site uses the name 芥川城. The site was chosen as No. 159 of the Continued Japan 100 Castles in 2017. Near the main bailey, a small shrine still honors Miyoshi Nagayoshi, who made the castle his base.

From JR Takatsuki Station take a Takatsuki city bus to the Tsukawaki stop, then walk about 25 minutes to the summit of Mount Miyoshi. There is no parking lot nearby; by car, follow Prefectural Route 6 from the Imajōchō intersection on National Route 171 toward Settsu-kyō. The mountain path starts on the east side of the eastern bailey group.

Excavations at the honmaru on the summit found a 4.2-metre-square building with foundation stones and roof tiles, likely a storehouse built under Miyoshi Nagayoshi. Over 200 objects came to light, including lamp dishes, tenmoku tea bowls, an inkstone and grinding bowls, showing the summit was a living and governing space, not just a storeroom.