The Staten Island Ferry is a passenger ferry route operated by the New York City Department of Transportation. The ferry's single route runs 5.2 miles (8.4 km) through New York Harbor between the New York City boroughs of Manhattan and Staten Island, with ferry boats making the trip in about 25 minutes. The ferry operates 24 hours a day, 7 days a week, with boats leaving every 15 to 20 minutes during peak hours and every 30 minutes at other times. It is the only direct mass-transit connection between the two boroughs. Historically, the Staten Island Ferry has charged a relatively low fare compared to other modes of transit in the area; and since 1997 the route has been fare-free. The Staten Island Ferry is one of several ferry systems in the New York City area and is operated separately from systems such as NYC Ferry and NY Waterway.

The Staten Island Ferry route terminates at Whitehall Terminal, on Whitehall Street in Lower Manhattan, and at St. George Terminal, in St. George, Staten Island. At Whitehall, connections are available to the New York City Subway and several local New York City Bus routes. At St. George, there are transfers to the Staten Island Railway and to the St. George Bus Terminal's many bus routes. Using MetroCard fare cards, passengers from Manhattan can exit a subway or bus on Whitehall Street, take the ferry for free, and have a free second transfer to a train or bus at St. George. Conversely, passengers from Staten Island can freely transfer to a subway or bus in Manhattan after riding the ferry.

The Staten Island Ferry originated in 1817, when the Richmond Turnpike Company started a steamboat service from Manhattan to Staten Island. Cornelius Vanderbilt bought the Richmond Turnpike Company in 1838, and it was merged with two competitors in 1853. The combined company was in turn sold to the Staten Island Railroad Company in 1864. The Staten Island Ferry was then sold to the Baltimore and Ohio Railroad in 1884, and the City of New York assumed control of the ferry in 1905.

In the early 20th century, the city and private companies also operated ferry routes from Staten Island to Brooklyn. Owing to the growth of vehicular travel, all of the routes from Staten Island to Brooklyn were decommissioned by the mid-1960s; but popular demand preserved the route to Manhattan. By 1967, the Staten Island-to-Manhattan ferry was the only commuter ferry within the entire city. A fast ferry route from Staten Island to Midtown Manhattan ran briefly from 1997 to 1998; proposals to revive the route resurfaced in the 2010s.

With 23.9 million riders in fiscal year 2016, the Staten Island Ferry is the busiest ferry route in the United States and the world's busiest passenger-only ferry system, thanks largely to the lack of other transit connections between Staten Island and the other boroughs. The ferry is also popular among tourists and visitors due to the free-of-charge views of the New York Harbor a trip provides. The ferry has been featured in several films.