Eastport is a hamlet and census-designated place (CDP) in Suffolk County, New York, on the South Shore of Long Island. The population was 1,831 at the 2010 census.

Eastport town is built on Shinnecock land. The present hamlet dates to 1772, when two men built the dam that formed what has come to be called the West Pond, which created a dividing line between Brookaven and Southampton. They built two mills below the dam, a saw mill and a gristmill. By 1845, the area to the east of the West Pond had come to be known as Waterville. The land to the west was called Seatuck, after a nearby creek. When, in 1860, the United States Postal Department needed to define the town to deliver mail, it combined the two areas. The name Seatuck was dropped for being too similar to Setauket, New York and the combined area was named Eastport.

Eastport was long and best known as the center of Long Island's duck industry. The first duck farms were established in the area in the 1880s. In the first half of the 20th century it was the capital of the production of Long Island ducks, producing 6.5 million ducks a year from 29 farms going to market. By 1915, the Long Island Duck Growers' Association was located in Eastport; and, in 1949, Cornell University established the Duck Disease Research Laboratory there. Routine surveillance carried out by the Duck Disease Research Laboratory identified the first case of Duck hepatitis virus (DHV-1) in the United States 1949 and, in 1967, the first case of Duck plague on the American Continent.

Practically all duck farms have been phased out and the descendants of the original farmers sold the valuable waterfront property for residential development projects.

Eastport straddles the border of the towns of Brookhaven and Southampton.

According to the United States Census Bureau, the CDP has a total area of 5.4 square miles (14.0 km), of which 5.3 square miles (13.6 km) is land and 0.12 square miles (0.3 km), or 2.41%, is water.

Historical population

Census	Pop.	Note	%±
2020	2,219		—
U.S. Decennial Census

According to the 2020 census, there were 2,219 people, 656 households and 544 families residing in the CDP. The population density was 264.7 inhabitants per square mile (102.2/km). There were 637 housing units at an average density of 116.0 per square mile (44.8/km). The racial makeup of the CDP was 89.48% White, 1.75% Black or African American, 0.48% American Indian, 1.11% Asian, 7.08% from other races, and 7.56% from two or more races.

There were 656 households and 767 housing units, with 83.23% as married couples living together. 12% of residents live alone, within which, 10.4% are 65 years of age or older. The average household size was 3.00 and the average family size was 3.24.

According to the 2021 American Community Survey, the population decreased slightly from the 2020 census, down to 2,095 people. The age distribution was: 19.9% under the age of 18, 4.9% from 18 to 24, 24.1% from 25 to 44, 28.5% from 45 to 64, and 22.7% who were 65 years of age or older. The median age was 45.3 years. For every 100 females, there were 90.6 males. Hispanic or Latino of any race were 12.6% of the population.

The median income was $121,250 and the median family income was $138,333. The per capita income for the CDP was $45,891. 6.01% of the population were below the poverty threshold, with 3.34% of those aged 60 or over.

Eastport is located within the Eastport-South Manor Central School District.

• Scott Disick, American media personality and socialite

• Eastport, New York: World War I Monument: Globe Strutting Doughboy (Roadside America.com)