The Raseborg Castle, is a medieval castle in Raseborg, Finland.
It has been suggested that the castle was founded by Hermann of Dorpat, the successor of Albert of Riga, and Livonian Brothers of the Sword after Livonian Crusade. They would have named the castle Ratzeburg after Bishopric of Ratzeburg.The castle is also suggested to be founded by Bo Jonsson Grip and it is thought that the castle's first phase was completed sometime between 1373 and 1378.
The first written data about the castle is from 1378. Its main purpose was to protect Sweden's interests in southern Finland against the Hanseatic city of Tallinn. The castle was originally built on a small island in the north end of a sea bay. The historians think that the castle was built in 3 different stages over time from the 14th to the 16th century.