Peconic is a census-designated place (CDP) that roughly corresponds to the hamlet by the same name in the Town of Southold in Suffolk County, New York, United States.

During the late 1800s and early 1900s, it was home to the Peconic School, an artist colony initially led by painters Benjamin Rutherfurd Fitz, Edward August Bell, Henry Prellwitz and Edith Mitchill Prellwitz.

[3] Albert Einstein was staying in Peconic in 1939 when he signed the famous Einstein–Szilárd letter to President Franklin Delano Roosevelt.

Goldsmith's Inlet was the site of a tidal mill that was improved with a windmill in 1870.

22.1% of all households were made up of individuals, and 10.8% had someone living alone who was 65 years of age or older.