.au Domain Administration (auDA) is the policy authority and industry self-regulatory body for the .au domain, which is the country-code top-level domain (ccTLD) for Australia. It was formed in 1999 to manage the .au ccTLD with the endorsement of the Australian Government and the authority of the Internet Corporation for Assigned Names and Numbers (ICANN). It is a not-for-profit membership organisation that promotes and protects the .au domain space.

The operation of the .au ccTLD began in 1986 with the delegation of .au administration to Robert Elz of the University of Melbourne by the Internet Assigned Numbers Authority (IANA). Elz devised the second-level domain (2LD) name structure, including .com.au, .net.au, .edu.au and .org.au, and introduced policies concerning eligibility for these domains. These policies included reserving the .com.au 2LD for registered commercial entities trading in Australia, and only being able to register a domain that closely aligned with a registrant's commercial name. Elz was responsible for the day-to-day operation of the .au ccTLD with all services provided free. By 1996, as businesses realised the commercial potential of the Internet, management of registrations became too great a job for Elz to accomplish by himself. Elz licensed the .com.au 2LD operation exclusively to Melbourne IT, the commercial arm of the University of Melbourne, for a term of five years.

Elz did not charge for domain services, but Melbourne IT ran domain registration on a for-profit basis, charging between $125–150 per year for registrations. Melbourne IT intended to remove the registration of pre-existing .com.au names whose owners had not paid registration fees by March 1997. This prompted ISP iiNet to file a class-action lawsuit on behalf of .com.au domain holders. iiNet withdrew this action when Melbourne IT assured them it would not remove existing domains until at least October 1997, when competition in the .com.au administration was expected to exist.

However, disenchantment in the way the .au domain was run persisted, leading to demand for a single regulatory body to oversee the namespace.

See .oz for the early history of .oz.au.

In recognition of the deteriorating state of .au, the Australian Internet community – primarily through several key industry associations and personalities – held a series of forums to work out a way forward. The result of this period of collaboration was the establishment in June 1997 of a new policy development body called Australian Domain Name Administration, or ADNA tasked with taking control of .au and operating the domain space for the public good.

ADNA, however, was marked by internal conflicts. After two years of internal struggles, ADNA was renamed .au Domain Administration (auDA) and adopted a new constitution, procedures, and board. The Department of Communications, Information Technology and the Arts set objectives for the new auDA board to reach in order for the new entity to gain endorsement as an industry self-regulatory body, endorsement achieved in December 2000.

The inaugural board of the new organisation was elected in April 1999, and began the task of trying to help mould a new framework of policies for the .au domain space. As part of the process, the organisation obtained a reassignment of management of the .au domain space from the Internet Corporation for Assigned Names and Numbers (ICANN), which had absorbed the responsibility for global root domain administration from IANA. This was the first formal agreement ICANN ever signed with a ccTLD operator. With the endorsement of the Australian Government and ICANN, auDA became the recognised ccTLD body for the .au domain space.