Big Run is a tributary of Little Muncy Creek in Lycoming County, Pennsylvania, in the United States.

[1] Big Run joins Little Muncy Creek 14.22 miles (22.88 km) upstream of its mouth.

[1] The surficial geology along the valley floor in parts of the middle or upper reaches of Big Run mostly consists of alluvium, which contains stratified sand and gravel.

[4] A concrete stringer/multi-beam or girder bridge carrying State Route 2015 over Big Run was built 1 mile (1.6 km) north of Lairdsville in 1929 and is 32.2 feet (9.8 m) long.

A concrete tee beam bridge carrying a township road and Pennsylvania Route 118 over the stream was built in Lairdsville in 1937 and is 33.1 feet (10.1 m) long.

[6] In January 2011, Chief Gathering LLC., a subsidiary of Chief Oil & Gas, received a $34,000 fine from the Pennsylvania Department of Environmental Protection for discharging approximately 25,200 US gallons (95,000 L) of hydrostatic testing water into the watershed of Big Run during a pipeline testing project in August 2010 in Penn Township.