Water Mill is a hamlet and a census-designated place (CDP) within the Town of Southampton on Long Island in Suffolk County, New York, United States.

[5] In 1644, England gave Edward Howell 40 acres (16 ha) of land near the new settlement of Southampton to build a mill for settlers to grind their grain into meal.

[6] Today, the hamlet boasts its status as the only settlement on the South Fork of Long Island with both a functioning watermill and windmill.

Today Water Mill is a resort community of beautiful beaches, farms and mega mansions.

Celebrities and public figures such as Richard Gere, Jennifer Lopez, Matt Lauer, Senator Frank Lautenberg, Steven Schwartzman and Bruce Blakeman own homes or have vacationed there.

Louise Fitzhugh's young adult novel The Long Secret takes place in Water Mill.