Hammersley Fork (also known as Hammersley Fork Creek) is a tributary of Kettle Creek in Potter County and Clinton County, Pennsylvania, in the United States. It is approximately 10.0 miles (16.1 km) long and flows through Warton Township in Potter County and Leidy Township in Clinton County. The watershed of the stream has an area of 32.7 square miles (85 km2). The main rock formation in the watershed is the Pottsville Formation.