| Koga Castle 古河城 | |
|---|---|
| Koga, Ibaraki Prefecture, Japan | |
  Koga Castle 古河城  Koga Castle 古河城 | |
| Coordinates | 36°11′12.8″N 139°41′43.7″E / 36.186889°N 139.695472°E |
| Type | flatland-style Japanese castle |
| Site information | |
| Condition | ruin |
| Site history | |
| Built | Muromachi period |
| Built by | Doi clan |
| In use | Edo period |
| Demolished | 1873 |
Koga Castle (古河城, Koga-jō) was a Japanese castle located in Koga, Ibaraki Prefecture, Japan. During the Muromachi period, Koga was the seat of the Kantō kubō, under the Ashikaga clan. At the end of the Edo period, Koga Castle was the administrative center of Koga Domain, which was held by a large number of fudai daimyō clans, spending the longest time under the control of the Doi clan (1633-1681, 1762–1871).