Spencer Run (also known as Spencer's Run) is a tributary of West Creek in Columbia County, Pennsylvania, in the United States. It is approximately 2.1 miles (3.4 km) long and flows through Jackson Township and Benton Township. The watershed of the stream has an area of 2.07 square miles (5.4 km2). Wild trout naturally reproduce in the stream. The surficial geology in the area mainly features Illinoian Till, Illinoian Leg, alluvium, colluvium, and bedrock.