Greenville is a town in Piscataquis County, Maine, United States. The population was 1,437 at the 2020 census. The town is centered on the lower end of Moosehead Lake, the largest body of fresh water in the state. Greenville is the historic gateway to the north country and a center for outdoor recreation in the area. Greenville High School, with 89 students, was ranked as the third best high school in Maine and one of the top 1,000 in the US in 2010.