The Babylon Branch is a rail service operated by the Long Island Rail Road in the U.S. state of New York. The term refers to the trains serving Montauk Branch stations from Valley Stream east to Babylon; in other words, the Babylon Branch is a rail service rather than an actual track. The electrification of the Montauk Branch ends east of the Babylon station, so the Babylon Branch is mostly served by electric trains.

The Long Island Rail Road, often abbreviated as the LIRR, is a railroad in the southeastern part of the U.S. state of New York, stretching from Manhattan to the eastern tip of Suffolk County on Long Island. The railroad currently operates a public commuter rail service, with its freight operations contracted to the New York and Atlantic Railway. With an average weekday ridership of 354,800 passengers in 2016, it is the busiest commuter railroad in North America. It is also one of the world's few commuter systems that runs 24/7 year-round. It is publicly owned by the Metropolitan Transportation Authority, which refers to it as MTA Long Island Rail Road. In 2023, the system had a ridership of 75,186,900, or about 253,800 per weekday as of the fourth quarter of 2023.