East Fallowfield Township is a township in Chester County, Pennsylvania, United States. The population was 7,626 at the 2020 census.

Ercildoun, population about 100, is an unincorporated community in East Fallowfield Township, Chester County, Pennsylvania, United States. The hamlet was founded by Quakers and was an early center of the abolitionist movement. In 1985 the entire hamlet, including 31 properties, was listed as a historic district on the National Register of Historic Places. Of these properties two were vacant land, 14 were significant buildings, ten were contributing buildings, and five buildings, built in the 1950s, were non-contributing. The Lukens Pierce House, an octagon house listed separately on the U.S. National Register of Historic Places, is located about half a mile northwest of the hamlet. Ercildoun is one of about ten hamlets in the township, which has no cities or towns, but has 31 sites listed on the National Register. It is one of the larger hamlets, located near the center of the township, and historically among the best known. The city of Coatesville is about 3 miles north.