Orr's Island is an island in Casco Bay and the Gulf of Maine, part of the Atlantic Ocean. The island is within the town of Harpswell, Maine, U.S., and forms an archipelago with Sebascodegan Island (also known as Great Island) to its north and Bailey Island (reached by the Bailey Island (or Cribstone) Bridge) to its south.
Orr's Island is connected to Great Island by the Orr's Island/Great Island Bridge, and is connected to the town of Brunswick on the mainland by Route 24 north over the Gurnet Bridge. Bowdoin College operates a 118-acre (48 ha) coastal studies center on Orr's Island.
As of 2000, Orr's Island had an estimated population of 752 people. 49.2% of the population were male, and 50.8% of the population was female. 98.1% of the population were white, 1.1% were Asian, 0.5% were two or more races, and 0.3% were some other race. Additionally, 83.9% of the population was 18 years or older, 23% were 65 years or older, and 4.3% were under 5 years of age.