Gerritsen Beach is a neighborhood in the New York City borough of Brooklyn, located near Marine Park and Sheepshead Bay. The area is served by Brooklyn Community Board 15.

Gerritsen Beach lies on a peninsula in the southeastern part of Brooklyn, near Marine Park; it is bounded on the north by Avenue U, to the east by Gerritsen Avenue, to the south by the Plumb Beach Channel, and on the west by Shell Bank Creek and Knapp Street. It is bisected, from west to east, by the Gotham Avenue Canal. The area north of the canal, known as the "new section" by local residents, has traditional city streets lined with stores, brick houses, and wide sidewalks; the elementary school, P.S. 277 ("The Gerritsen Beach School"), is also north of the canal. The area south of the canal (the "old section") is a popular spot for party boats and chartered fishing boats to be berthed. The streets in Gerritsen Beach are in alphabetical order (that is, Aster, Bevy, Celeste, Dictum, etc.), and they are patrolled by officers of the New York Police Department's 61st Precinct.

The neighborhood is named for Wolphert Gerretse, a Dutch settler, who, in the early seventeenth century, built a house and mill on Gerritsen Creek (which is now part of the nearby Marine Park neighborhood). The three-hundred-year-old mill was destroyed by fire in 1931.

Until the early twentieth century, the area remained undeveloped except for a few squatters’ bungalows clustered at the foot of Gerritsen Avenue. In 1920, Realty Associates, a speculative real-estate builder, began constructing a middle-class summer resort there. The southwestern section of Gerritsen’s meadow was soon covered by one-story bungalows with peaked roofs and no backyards; typically, these houses were built on tiny 40-by-45-foot lots. The popularity of this venture spurred further growth. Some bungalow-owners made them suitable for year-round habitation; others built two-story houses with backyards; and, within a decade, there were fifteen hundred houses in Gerritsen Beach.

The neighborhood has a large Irish-Catholic presence in the community. A few long-standing residents of Irish descent refer to the community as being cois farraige, which is an Irish language phrase meaning "by the sea". The remaining percentage of the population is predominantly of Italian and German descent.

Resurrection Roman Catholic Elementary School operated until the end of the 2004-2005 school year when it was closed by the diocese. Currently, the Brooklyn Blue-Feather School for special-needs children operates in the former Resurrection school building. The neighborhood is also home of the New York City Department of Education's Public School 277 (P.S. 277), an elementary school known simply as "the Gerritsen Beach School".

The Gerritsen Ballfields, consisting of three baseball fields, two athletic fields for soccer or football, and one Little League field, are located on the east side of Gerritsen Avenue. In 1993, this site benefitted from a $192,000 renovation sponsored by Borough Council Member Herbert E. Berman. The park area also supports a "mini-airport" for motorized model airplanes; it is located at Seba Avenue and Gerritsen Avenue.

Recreational fishing is very popular with citizens of the community. Anglers can be found fishing along the shore at the southern end of Gerritsen Avenue and along the adjacent shoreline of the Gerritsen Creek-Marine Park "salt marsh". The Gerritsen Creek estuary and the adjacent salt marsh is also a major spawning ground for various species of marine fish. Riding of quads is also popular, as people ride around the beach and in the trails.

The community is serviced by the New York City Transit bus B31, and the BM4 express bus.

Resurrection Roman Catholic Church and St. James Evangelical Lutheran Church both serve the community.

The local Volunteer Fire Department (a.k.a. "the Vollies"), the last remaining volunteer fire department in Brooklyn, was organized in 1922 when Gerritsen Beach was a small summer-resort community. The name of the department is officially spelled Gerrittsen Beach Fire Department. In 1921, a damaging fire on Abbey Court demonstrated to the community that the city’s regular fire apparatus could not reach the beach in time to put out a fire. A mass meeting was called by the residents, and that resulted in the organization of the only volunteer fire department in Brooklyn.

Before the city added water mains under Gerritsen Beach streets, the Volunteers had to handle fires at least three times a week. The danger posed to Gerritsen Beach residents by fire was especially acute because most families relied on oil stoves and kerosene lamps, and the water to fight fires had to be pumped from wells. The city did not build Engine Company 321's firehouse at Gerritsen Avenue and Avenue U until October 4, 1930.

Members of the fire brigade, currently known as the Vollies, were, in earlier times, nicknamed "the Vamps". Members are not only trained to fight fires, but also to rescue people who are drowning and to assist in other medical emergencies. According to the Vollies 1976 anniversary booklet, the Vollies were approved by the New York State Department of Health as an Emergency Services Training Center. Although the community is now served by Engine Company 321, strong support for the "Vollies" continues.

The following historical events involved the Gerritsen Beach volunteers in actions outside their own neighborhood:

The Gerrittsen Beach Volunteer Fire Department has one fire engine, one ambulance, and one rescue vehicle.

ATURA  Barren Island  Bath Beach  Bay Ridge  Bedford  Bedford-Stuyvesant  Bensonhurst  Bergen Beach  BoCoCa  Boerum Hill  Borough Park  Brighton Beach  Brooklyn Chinatown  Brooklyn Heights  Brownsville  Bushwick  Canarsie  Carroll Gardens  City Line  Clinton Hill  Cobble Hill  Coney Island  Crown Heights  Cypress Hills  Ditmas Park  Downtown  Dumbo  Dyker Heights  East Flatbush  East New York  East Williamsburg  Farragut  Fiske Terrace  Flatbush  Flatlands  Fort Greene  Fort Hamilton  Fulton Ferry  Georgetown  Gerritsen Beach  Gowanus  Gravesend  Greenpoint  Greenwood Heights  Highland Park  Homecrest  Kensington  Little Poland  Madison  Manhattan Beach  Mapleton  Marine Park  Midwood  Mill Basin  Navy Yard  New Lots  New Utrecht  Ocean Hill  Ocean Parkway  Park Slope  Pigtown  Plum Beach  Prospect Heights  Prospect Lefferts Gardens, Brooklyn  Prospect Park South  RAMBO  Red Hook  Sea Gate  Sheepshead Bay  South Park Slope  Starrett City  Stuyvesant Heights  Sunset Park  Vinegar Hill  Weeksville  White Sands  Williamsburg  Windsor Terrace  Wingate