Setauket /səˈtɔːkɪt/ is a hamlet and census-designated place (CDP) in the Town of Brookhaven, Suffolk County, New York, United States, on the North Shore of Long Island.

The name "Setauket" is derived from the historic Algonquian-speaking Setalcott Indians, who had lived in the area prior to its colonial period.

This change was facilitated by Captain John Scott, a professional mercenary hired to clear out the Native American Indians.

A crafty land speculator, Scott claimed at one point to own a third of the island, including the Setauket area.

Despite the questionable nature of many of his claims, John Scott had enough power and support to rename Setauket for his ancestral homeland in England, Ashford, Kent, and to construct a stately home named Egerton.

A Patriot force led by General Samuel Holden Parsons sailed across Long Island Sound from Fairfield, Connecticut, proposing to attack the Loyalists.

From 1778 to 1781, the Culper Spy Ring passed information about British troop movements gathered in New York City to George Washington.

The spy ring consisted primarily of Setauket residents, including its leader Benjamin Tallmadge and key agent Abraham Woodhull.

Shipbuilding, which had begun as early as 1662, prospered as new shipyards populated the section of Setauket Harbor known as Dyers Neck.

(At that time Brooklyn was considered part of Long Island, and the largest sailing vessel built at Port Jefferson, the Martha E. Wallace of 1902, was a schooner.)

Better known is the famous, or infamous, schooner yacht Wanderer built at Setauket in 1857 by William J. Rowland at the direction of captain Thomas B. Hawkins who would later command her.

The Wanderer was sold to new owners after her first cruise, and they tried to have the vessel secretly converted into a slaver at Port Jefferson in 1858, largely employing outsiders.

Suspicious residents alerted authorities, and the vessel was captured by the USRC Harriet Lane off Port Jefferson as it attempted a hasty departure.

Sadly, authorities in New York returned the vessel to its owners, and she later completed what is considered the last successful American slaving voyage to Africa.

Following the 1873 completion of railroad service from New York City to Port Jefferson, the Setaukets began functioning as a summer resort town.

In the post-World War II era, Setauket experienced a population boom, as the remaining agricultural lots were filled in with residential developments.

Melville also created a New England–style village district in neighbouring Stony Brook, being the closest commercial hub to Setauket's western areas and complementing the role of Port Jefferson to the east.

East Setauket is home to Renaissance Technologies, one of America's most profitable hedge funds, which was founded by Stony Brook University mathematics professor James Harris Simons.

The Greek Orthodox Monastery of the Holy Cross, headquarters of the Jerusalem Patriarchate in America, is located in Setauket.

Setauket is the principal setting of the AMC television drama Turn: Washington's Spies, which premiered in 2014 and tells the story of the Culper Ring.