The United States Army Rangers, according to the U.S. military, are limited to those who served in designated U.S. Army Ranger units, past or present.However, the term is often used to include those who are graduates of the U.S. Army Ranger School, even though they did not serve in a Ranger unit.

The term ranger has been in use unofficially in a military context since the early 17th century. The first military company officially commissioned as rangers were New England soldiers fighting in King Philip's War (1676) and from there the term came into common official use in the French and Indian Wars. There have been American military companies officially called Rangers since the American Revolution.