Fukuoka Castle is a Japanese castle located in Chūō-ku, Fukuoka, Japan. It is also known as Maizuru Castle or Seki Castle (石城 Seki-jō). Completed in the early Edo period for tozama daimyo Kuroda Nagamasa, it has been decreed a historic site by the Japanese government.
The castle lies in the centre of Fukuoka, on top of Fukusaki hill. The Naka River, Naka-gawa in Japanese, acts as a natural moat on the eastern side of the castle, while the western side uses a mudflat as a natural moat. Hakata, a ward with a bustling port, is located on the opposite side of the Naka River to the east. The castle town was established on the northern side, facing the sea.
Much of the castle grounds has been converted to Maizuru Park, which houses several sports facilities, a courthouse, and an art museum. Heiwadai Baseball Stadium, the past home field of the Nishitetsu Lions and the Fukuoka Daiei Hawks, was also located on the castle grounds. Some of the castle's gates as well as its towers and turrets, known as yaguras, are preserved inside the park, one of which has been marked as an important historical artifact by the Japanese government.
The remnants of a korokan, an ancient guest house for foreign diplomats, were discovered under the castle grounds in 1987, showing that the castle was a vital geographical checkpoint even into the Heian period. This is the only korokan remnant found in all of Japan.