Mount Kelsey rises in northern New Hampshire, in western Millsfield with its western slopes extending into Erving's Location. Part of its summit area is occupied by the Granite Reliable Wind Farm, and the mountain is accessible by road from the Phillips Brook watershed to the south. It stands on a local drainage divide, making it significant in the region’s watershed geography. Water from its north side flows through the West Branch of Clear Stream to the Androscoggin River and onward into Maine toward the Atlantic, while runoff from its southeast and west sides enters separate stream systems that ultimately reach either the Atlantic or Long Island Sound.