Lone Mountain is a peak in Ulster County, New York, within the Catskill Mountains and the Slide Mountain Wilderness of Catskill State Park. It stands near Table Mountain to the southwest and Rocky Mountain to the east. The mountain is notable for straddling two major drainage systems. Its southeast slopes feed Rondout Creek, whose waters flow to the Hudson River and New York Bay. Its west and north slopes drain through Donovan Brook and the East Branch of the Neversink River into the Delaware River system, eventually reaching Delaware Bay.