Prerogative instruments are an ancient form of lawmaking inherited from England. They are created by the Governor-General or monarch, without reference to Parliament, under the royal prerogative, a power of the Crown that still exists and has not been superseded by parliamentary legislation.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 the recent ones are also available on the Federal Register of Legislation. They are sometimes called letters patent.