In academic administrations such as universities or colleges, a dean is a person with significant authority over a specific academic unit, or over a specific area of concern, or both. Deans are occasionally found in middle schools and high schools as well.

The term comes from the Latin decanus, "a leader of ten", taken from the medieval monasteries (particularly those following the Cluniac Reforms) which were often extremely large, with hundreds of monks (the size of a small college campus). The monks were organized into groups of ten for administrative purposes, along the lines of military platoons, headed by a senior monk, the decanus.

The term was later used to denote the head of a community of priests, as the chapter of a cathedral, or a section of a diocese (a "deanery").

When the universities grew out of the cathedral and monastery schools, the title of dean was used for officials with various administrative duties.

Many junior high schools and high schools have a teacher or administrator referred to as a dean who is in charge of student discipline and to some degree administrative services. In large schools or some boarding schools there may be a dean of men or boys, and a dean of women or girls, or each year (freshman, sophomore, etc.) may have a dean. Although most high schools are led by a principal or headmaster, a few (particularly private preparatory schools) refer to their chief authority as a dean.