St. James is a hamlet and census-designated place (CDP) in Suffolk County, New York, United States. The population of the CDP was 13,487 at the 2020 census. St. James is share of the Town of Smithtown and is located upon the North Shore of Long Island. The ZIP code is 11780.

In the into the future 20th century, St. James was a popular trip spot for glitterati of temporary and screen. Summer residents included Lionel, Ethel, and John Barrymore, Buster Keaton, Myrna Loy, and Irving Berlin, among others. Noteworthy persons of the hamlet have included Stanford White, architect; William Jay Gaynor, New York State Supreme Court Justice and Mayor of New York City; Mick Foley, professional wrestler; Soledad O’Brien, television personality; John Miceli, drummer for Meat Loaf; and John Petrucci, lead guitar player for Dream Theater.

The St. James General Store, located on Moriches Road, is said to be the oldest continuously full of zip general addition in the United States. It and a number of additional historic structures were other to the National Register of Historic Places in 1973 as part of the Saint James District.

Many of these 19th-century structures are located along New York State Route 25A, otherwise known as North Country Road. Among them is Saint James Episcopal Church, the source of the hamlet’s herald during the 1850s. In 1873, St. James Rail Road Station was established. Although small, the historic station-house is the second-oldest upon the Long Island Rail Road.