A veteran (from Latin vetus 'old') is a person who has significant experience (and is usually adept and esteemed) and expertise in a particular occupation or field. A military veteran is a person who is no longer in a military.

A military veteran that has served directly in combat in a war is further defined as a war veteran (although not all military conflicts, or areas in which armed combat took place, are necessarily referred to as wars).

Military veterans are unique as a group as their lived experience is so strongly connected to the conduct of war in general and application of professional violence in particular. Therefore, there are a large body of knowledge developed through centuries of scholarly studies that seek to describe, understand and explain their lived experience in and out of service. Griffith with colleagues provides an overview of this research field that addresses veterans general health, transition from military service to civilian life, homelessness, veteran employment, civic engagement and veteran identity as recurrent investigative topics in the field.