Muncy is a borough in Lycoming County, Pennsylvania, in the United States. The name Muncy comes from the Munsee Indians who once lived in the area. The population was 2,663 at the 2000 census. It is part of the Williamsport, Pennsylvania Metropolitan Statistical Area. Muncy is located on the West Branch Susquehanna River, just south of the confluence of Muncy Creek with the river.