The Castle of the Island of Loreto, also known as Castello dell'Isola di Loreto, is a fortress located on a small island in the Gulf of La Spezia, Italy. The castle was built in the 16th century to protect the city of Portovenere and the Gulf of La Spezia from pirate attacks. It was also used as a prison until the 19th century.

The castle has a unique pentagonal shape and is surrounded by water on all sides. It is accessible only by boat and visitors can take a guided tour of the castle. The tour includes a visit to the rooms and chambers of the castle, including the prisons and the torture chamber, as well as the weapons room, which displays various weapons and armors used in the past.

Today, the Castle of the Island of Loreto is a popular tourist attraction and a cultural center, hosting various exhibitions and events. Its location on the small island and its unique architecture make it a picturesque spot for photography and sightseeing.