Takamatsu Castle (高松城, Takamatsu-jō) is a Japanese castle located in central Takamatsu, Kagawa Prefecture, on the island of Shikoku, Japan. It is also called Tamamo Castle (玉藻城, Tamamo-jō), literally "seaweed castle," for its seawater moats. The castle was headquarters of the Takamatsu Domain, which ruled eastern Sanuki Province (modern-day Kagawa) from 1588 to 1869. It is now a park. The castle site has been a National Historic Site since 1955. This castle is one of three in Japan to use seawater moats, along with Imabari Castle in Ehime Prefecture and Nakatsu Castle in Ōita Prefecture.