An alumn (with a silent "n"), alum, alumnus, or alumna is a former student of a college, university, or school. The term is often used synonymously with "graduate." Alumni reunions are a popular event at many institutions. They are organized by alumni associations and are often social occasions for fundraising.

In Latin, alumnus is the masculine singular form and alumna is the feminine singular form. (The words are derived from the Latin verb alere, "to nourish," and literally mean "nourished one" or "nursling.") These terms are recommended by leading English-language dictionaries, but because they are gender-specific, their use can be limited. The Latin plural is alumni for men and mixed groups and alumnae for women. The gender-neutral English term alumn/alum, created by clipping from alumnus, is also used, along with its plural alumns/alums.

Recently, the definition of "alum" has expanded to include people who have "matriculated at" or exited from any kind of organization or process. As such, one can potentially be a "corporate alum" of XYZ Company, or an alum of a military branch, non-profit organization, or training process.

Educational institutions tend to follow Latin usage: alumnus for males, alumna for females, and alumni for mixed groups. All-women colleges use alumna and alumnae. Some institutions, such as Texas A&M University, do not refer to their graduates as "alumni" or even "graduates," choosing to use the term "former students."

In the United Kingdom, the phrases old boy and old girl are sometimes used for former students.

See also:

• Alma mater
• Old boy network