The Staten Island Railway (SIR) is a rapid transit line in the New York City borough of Staten Island. It is owned by the Staten Island Rapid Transit Operating Authority (SIRTOA), a subsidiary of the Metropolitan Transportation Authority, and operated by the New York City Transit Authority Department of Subways. SIR operates 24 hours a day, seven days a week, providing local service between St. George and Tottenville, along the east side of the island. There is currently only one line on the island, and there is no direct rail link between the SIR and the New York City Subway system, but SIR riders do receive a free transfer to New York City Transit bus and subway lines, and the line is included on official New York City Subway maps. Commuters on the railway typically use the Staten Island Ferry to reach Manhattan. The line is accessible from within the Ferry Terminal, and most of its trains are timed to connect with the ferry. In 2023, the system had a ridership of 6,151,400, or about 19,500 per weekday as of the fourth quarter of 2023.

Staten Island is the southernmost borough of New York City, coextensive with Richmond County and situated at the southern most point of New York. The borough is separated from the adjacent state of New Jersey by the Arthur Kill and the Kill Van Kull and from the rest of New York by New York Bay. With a population of 495,747 in the 2020 Census, Staten Island is the least populated New York City borough but the third largest in land area at 58.5 sq mi (152 km2); it is also the least densely populated and most suburban borough in the city.