Harrison is a town in Cumberland County, Maine, United States. The population was 2,730 at the 2010 census. A historic resort area, Harrison straddles Long Lake and Crystal Lake. It is part of the Portland–South Portland–Biddeford, Maine metropolitan statistical area.
The Massachusetts General Court granted Otis Field Plantation in 1771 to James Otis and other heirs of Captain John Gorham and his company for their service in the 1690 Battle of Quebec. It replaced a 1736 grant which had been ruled invalid. In 1797, the plantation was incorporated as Otisfield. On March 8, 1805, Harrison was set off and incorporated from portions of Otisfield and Bridgton. It was named after a principal landowner, Harrison Gray Otis of Boston, the heir of James Otis.
In the autumn of 1792, two brothers from Gorham, John and Nathan Carsley, built a camp and cleared land in Harrison. During the winter they returned to Gorham, coming back in March 1793 with their wives.