A distinctive unit insignia (DUI) is a metallic heraldic badge or device worn by soldiers in the United States Army. The DUI design is derived from the coat of arms authorized for a unit. DUIs may also be called "distinctive insignia" (DI) or, imprecisely, a "crest" or a "unit crest" by soldiers or collectors. The U.S. Army Institute of Heraldry is responsible for the design, development and authorization of all DUIs.

The Institute of Heraldry, officially The Institute of Heraldry, Department of the Army, is an activity of the Administrative Assistant to the Secretary of the Army solely responsible for furnishing heraldic services to the President of the United States and all federal government agencies. Title 18 of the United States Code, Chapter 33, Section 704 and Title 32 of the Code of Federal Regulations, Part 507 permit the institute to issue directives on how military insignia are displayed, the criteria for issuance, and how insignia will be worn on military uniforms.