Matinicus Isle is an island plantation in Knox County, Maine, United States. The island is located within Penobscot Bay about 20 miles east of the mainland coast and is accessible by state ferry service from Rockland or by air taxi from Knox County Regional Airport. Matinicus is the farthest inhabited land off the east coast into the Atlantic Ocean which is part of the United States. The plantation is both a year-round island community and a summer colony. The population was 53 at the 2020 census.