Rock Run is a tributary of Martins Creek in Lower Makefield Township in Bucks County, Pennsylvania in the United States.
Rock Run was entered into the Geographic Names Information System of the U.S. Geological Survey on 2 August 1979 as identification number 1185276. It is also listed in the Pennsylvania Gazetteer of Streams as identification number 02922.
Rock Run rises near Big Oak Road and Stony Hill Road in the southern portion of Lower Makefield Township at an elevation of approximately and is generally east oriented until river mile 2.87 where it makes a 90ð turn to the right flowing south as it receives a tributary from the left. After about a mile it then turns east, then south and southwest until it discharges at Martins Creek's 3.20 river mile.
Rock Run rises in the Felsic Gneiss formation laid during the Precambrian, light buff to pink and medium to fine grained rock, mineralogy includes quartz, microcline, pyroxene, and biotite. As it flows east, it runs into the Pensauken and Bridgeton Formations laid down during the Tertiary period, yellow to reddish brown feldspathic quartz sand, coarse gravel, and boulder. Then it finally flows into the Trenton Gravel Formation from the Quaternary, consisting of feldspathic quartz sand which is reddish brown, yellow, and white, with some beds of gravel.