Prerogative instruments are an ancient form of law making inherited from England and are instruments made by the Governor-General or monarch without reference to Parliament under the royal prerogative which is that power of the Crown still existing and not superseded by parliamentary legislation.

Prerogative instruments include instruments which establish national honours such as the Order of Australia, and the procedures for granting them. These instruments are usually published in the gazette and most recent ones are also available on the Federal Register of Legislation. They are sometimes called letters patent.