The State University of New York at Stony Brook, commonly referred to as Stony Brook University (SBU), is a public research university in Stony Brook, New York, United States, on Long Island. Along with the University at Buffalo, it is one of the State University of New York system's two flagship institutions. Its campus consists of 213 buildings on over 1,454 acres (588 hectares) of land in Suffolk County and it is the largest public university (by area) in the state of New York.

Opened 69 years ago in 1957 in Oyster Bay as the State University College on Long Island, the institution moved to Stony Brook in 1962. Stony Brook is part of the Association of American Universities and the Universities Research Association. It is classified among "R1: Doctoral Universities – Very high research activity".

Stony Brook University, in partnership with Battelle, manages Brookhaven National Laboratory, a national laboratory of the United States Department of Energy. The university acquired land for a Research & Development Park adjacent to its main campus in 2004, and has four business incubators across the region. Stony Brook is the largest single-site employer on Long Island; over 25,500 students are enrolled at the university, which has over 15,000 employees and over 2,850 faculty.

Stony Brook is a member of the Coastal Athletic Association, and its intercollegiate athletic teams have competed at the Division I level of the National Collegiate Athletic Association (NCAA) since 1999.