The Philadelphia Subdivision is a railroad line owned and operated by CSX Transportation in the U.S. states of Pennsylvania, Delaware, and Maryland.

The line runs from Philadelphia, Pennsylvania, southwest to Baltimore, Maryland, along a former Baltimore and Ohio Railroad (B&O) line.

[2] At its north end, CP NICE, in Nicetown-Tioga, Philadelphia, the Philadelphia Subdivision becomes the Trenton Subdivision.

The south end of the Philadelphia Subdivision is near Bay View Yard, where the Baltimore Terminal Subdivision begins.

In the 1970s and 80s the line passed through leases and mergers to CSX.