Islesboro is a town in Waldo County, Maine, United States, comprising Islesboro Island and several smaller islands. The population was 583 at the 2020 census. It has a summer colony accessible by state ferry service from Lincolnville Beach three miles to the west, by private boat, or by air taxi service. Home to Warren Island State Park, Islesboro includes the village of Dark Harbor.

Waldo County is a county in the state of Maine, United States. As of the 2020 census, the population was 39,607. Its county seat is Belfast. The county was founded on February 7, 1827, from a portion of Hancock County and named after Brigadier-General Samuel Waldo, proprietor of the Waldo Patent.