Little Diamond Island (previously Little Hog Island) is an island in Casco Bay, Maine. It is part of the city of Portland, Maine. As of the 2000 census, the island had a year-round population of 5. Most of the island is private property. It is served by the Casco Bay Lines ferry service.
At low tide, Little Diamond Island connects to Great Diamond via a semi-submerged sandbar. This is how the City of Portland is capable of picking up the trash on both islands. Little Diamond Island's water supply comes from the City of Portland, with the majority of the houses/cottages receiving their water through aboveground pipes. The aboveground pipes are turned off and emptied in the winter, leaving the south end of the island with no water.
As of February 2007, there are 55 homes/cottages on Little Diamond Island.