Karatsu Castle, Japanese castle in Karatsu, Saga Prefecture, Japan

Karatsu Castle is a hirayamajiro whose honmaru sits atop Mount Manto, with the ni-no-maru and san-no-maru laid out to the west and outer structures to the south. Its stone walls rise directly from Karatsu Bay, which serves as a natural moat. The present five-story donjon, a 1966 reconstruction, stands on the honmaru's stone base.

Terasawa Hirotaka, granted Karatsu in 1595, began the full-scale castle in 1602 and completed it in 1608, reusing stone and timber from the abandoned Nagoya Castle and having Kyushu daimyo dig the moats named after their domains. The keep foundation existed by 1627, but no tower was authorized. After the Terasawa line died out in 1647, five fudai clans held the domain, the Ogasawara last until 1871.

The honmaru was left without a donjon: records from 1627 show only the stone base, and no drawing or plan of a tower survives. The present five-storey keep, built in 1966, houses a museum whose exhibits include a large old Karatsu jar, a municipal important cultural property. The name Maizuru, dancing crane, comes from the beaches spreading either side like open wings.

From JR Karatsu Station the castle is a 15-minute walk, or take the Karatsu One-Line bus 4 to 8 minutes to the Karatsu Castle Entrance stop; the Showa bus from Fukuoka's Karatsu-go line ends at Takadono Pier, 5 minutes away on foot. A paid inclined elevator covers the 34 m climb from the foot of the hill to the upper Maizuru Park plaza. A paid municipal parking lot sits across the road in Higashijonai.

The present keep is not a reconstruction of a documented original: no drawing or plan of a donjon survives, and records from 1627 list only the stone base. The five-tier tower raised in 1966 follows an imagined Keichō-period design and houses a museum. Excavations have since found roof tiles bearing the same pattern as those of Nagoya Castle, whose materials were reused here.