Fidlers Run (also known as Fiddlers Run, Fidler Run, or Fidlers Creek) is a tributary of the Susquehanna River in Northumberland County, Pennsylvania, in the United States. It is approximately 3.1 miles (5.0 km) long and flows through Jackson Township and Lower Mahanoy Township. The watershed of the stream has an area of 6.88 square miles (17.8 km2). The stream is not designated as an impaired waterbody, although a reaches of a few of its unnamed tributaries are. It is a small stream, with a width of 3 to 5 feet (0.91 to 1.52 m). Large areas of agricultural land occur along a substantial portion of its length.