South Mountain is a mountain in Greene County, New York, in the Catskill region east of Haines Falls. It rises near other prominent local summits, including Roundtop Mountain to the southwest, and forms part of the rugged upland landscape that characterizes this section of the Catskills. Its watersheds link it to two notable nearby bodies of water, draining south toward Kaaterskill Creek and north toward North-South Lake. Together, its location, surrounding peaks, and drainage patterns place it within the distinctive mountain terrain of this part of New York.