Trainer is a borough in Delaware County, Pennsylvania, United States. The population was 1,828 at the 2010 census, down from 1,901 at the 2000 census. The borough was named after David Trainer, a wealthy textile manufacturer.
Trainer is named after the Linwood Mills owner David Trainer Sr. The borough of Trainer was originally part of Lower Chichester Township and was incorporated as a borough in 1919.
Trainer is located in southern Delaware County at 39°49′43″N 75°24′13″W (39.828612, -75.403599), on the northwest bank of the Delaware River. It is bordered to the southwest by the borough of Marcus Hook, to the west by the community of Linwood in Lower Chichester Township, to the north by Upper Chichester Township, to the east by the city of Chester, and to the south across the Delaware River by Gloucester County, New Jersey.
Stoney Creek passes through and mouths in the town.
U.S. Route 13 (Post Road) crosses the borough, leading northeast through Chester 18 miles (29 km) to Philadelphia and southwest 10 miles (16 km) to Wilmington, Delaware.
According to the United States Census Bureau, the borough has a total area of 1.4 square miles (3.6 km2), of which 1.0 square mile (2.7 km2) is land and 0.31 square miles (0.8 km2), or 22.94%, is water.
The shore of the Delaware River is heavily industrialized and is an extension of the Port of Chester. The Stoney Creek Secondary has a rail yard north of its namesake.