AUSA can refer to two different things:

1. The Association of the United States Army, which is a private, non-profit organization that serves as the professional association of the United States Army. It was founded in 1950 and has 121 chapters worldwide. Membership is open to everyone, not just Army personnel.

2. Assistant United States Attorney, which is an official career civil service position in the U.S. Department of Justice composed of lawyers working under the U.S. Attorney of each U.S. federal district. AUSAs are career civil servants who work as criminal prosecutors or represent the U.S. government in civil litigation. The National Association of Assistant U.S. Attorneys (NAAUSA) is the professional association for AUSAs.

Therefore, AUSA can refer to either a professional association for the United States Army or a career position for lawyers in the U.S. Department of Justice.