The Port Washington Branch is an electrified, mostly double-tracked rail line and service owned and operated by the Long Island Rail Road in New York, in the United States. It branches north from the Main Line at the former Winfield Junction station, just east of the Woodside station in the New York City borough of Queens, and runs roughly parallel to Northern Boulevard past Mets-Willets Point, Flushing, Murray Hill, Broadway, Auburndale, Bayside, Douglaston, Little Neck, and then crosses into Nassau County for stops in Great Neck, Manhasset, and Plandome before terminating at Port Washington.

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.