A graduate school (sometimes shortened as grad school) is a school that awards advanced academic degrees (i.e. master's and doctoral degrees) with the general requirement that students must have earned a previous undergraduate (bachelor's) degree with a high grade point average. A distinction is typically made between graduate schools (where courses of study vary in the degree to which they provide training for a particular profession) and professional schools, which offer specialized advanced degrees in professional fields such as medicine, nursing, business, engineering, or law. The distinction between graduate schools and professional schools is not absolute, as various professional schools offer graduate degrees (e.g., some nursing schools offer a master's degree in nursing). Also, some graduate degrees train students for a specific profession (e.g. an MSc or a PhD in epidemiology trains a person to be an epidemiologist).

Many universities award graduate degrees; a graduate school is not necessarily a separate institution. While the term "graduate school" is typical in the United States and often used elsewhere (e.g. Canada), "postgraduate education" is also used in some English-speaking countries (Australia, Canada, Ireland, India, Bangladesh, New Zealand, Pakistan and the UK) to refer to the spectrum of education beyond a bachelor's degree. Those attending graduate schools are called "graduate students" (in both American and British English), or often in British English as "postgraduate students" and, colloquially, "postgraduates" and "postgrads". Degrees awarded to graduate students include master's degrees, doctoral degrees, and other postgraduate qualifications such as graduate certificates and professional degrees.