Masteyra Island (, ) is a rocky island 700 m long in east-west direction and 200 m wide lying in Perrier Bay on the northwest coast of Anvers Island in the Palmer Archipelago, Antarctica. It is separated from Anvers Island to the east-southeast by a 1.13 km wide passage.
The island is named after the ancient Thracian settlement and fortress of Masteyra in Southern Bulgaria.
Masteyra Island is located at , 6.58 km south of Quinton Point, 4.21 km north of Vromos Island and 7.55 km east-northeast of Giard Point. British mapping in 1980.