private, coeducational institution of higher learning in Garden City, New York, U.S. Adelphi is a liberal arts college serving Long Island, with branch campuses in Manhattan and Huntington. It offers a range of bachelor's and master's degree programs in business, nursing, social work, and the arts and sciences. Doctorate degrees are offered in nursing, education, social work, and psychology. Total enrollment is about 7,000.

The regents of the University of the State of New York established the charter for Adelphi University on June 24, 1896, and instruction began in September of that year. The school was originally located in Brooklyn; it moved to Garden City in 1929. After 1912 the university admitted only women. However, the educational needs of servicemen returning from World War II required that Adelphi restore its original coeducational policy in 1946. The School of Nursing opened in 1943 and the School of Social Work in 1949. The graduate school in psychology, organized in 1951, was established as a separate school—the Gordon F. Derner Institute of Advanced Psychological Studies—in 1972; it was the first of its kind in the country.