Sesimbra Castle, also known as Castelo de Sesimbra, is a medieval castle located in the town of Sesimbra, Portugal. The castle was built in the 12th century by the Moors, and was later taken over by the Christians during the Reconquista in the 13th century.

The castle played an important role in the defense of the region, with its strategic position on a hill overlooking the town and the surrounding coastline. The castle was also a key point in the coastal defense system, along with the castles of Palmela and Almada.

Today, the castle is open to the public and visitors can explore the ramparts, towers, and courtyard. The castle also offers spectacular views of the town and the ocean. Inside the castle, there is a small museum with exhibits on the history of the castle and the region.