Matinicus Isle plantation is an archipelago located on the southeastern fringes of Penobscot Bay in the Gulf of Maine, part of the Atlantic Ocean. According to the United States Census Bureau, the plantation has a total area of , of which is land and is water. Matinicus Island, the largest land mass in the archipelago, spans approximately in length and in width for an area of about . The elevation ranges from 0 to 100 feet (30.5 m). Matinicus Isle is located approximately 1 mile (1.6 km) north of Criehaven Isle.