The Migration Act 1958 (Cth) is an Act of the Parliament of Australia that governs immigration to Australia. It set up Australia’s universal visa system (or entry permits). Its long title is "An Act relating to the entry into, and presence in, Australia of aliens, and the departure or deportation from Australia of aliens and certain other persons."

The 1958 Act replaced the Immigration Restriction Act 1901, which had formed the basis of the White Australia policy, abolishing the infamous "dictation test", as well as removing many of the other discriminatory provisions in the 1901 Act. The 1958 Act has been amended a number of times.

Deportation decisions, provided for in section 18 the Act, are at the absolute discretion of the responsible Minister or his delegate. Deportation requires a specific deportation order (section 206) and applies to Australian permanent residents only. Removal is an automatic process applying to persons held in immigration detention and does not require any specific order to be made. (Section 198) It covers those persons who do not have a valid visa to be in Australia, whether their valid visa has expired or was cancelled.

The original bill was introduced to the House of Representatives on 1 May 1958 by Alick Downer, the Minister for Immigration in the Menzies Government.

In 1966, the Holt government amended the Act through the Migration Act 1966. The amendments were relatively minor, dealing with decimalisation and identity documents for crew members of foreign vessels. Several sources have incorrectly identified the Migration Act 1966 as the vehicle through which the Holt government dismantled the White Australia policy. In fact, the government's actions in that area required no modification of the existing legislation, and were accomplished solely through ministerial decree.

The Migration Amendment Act 1983 substituted the words "immigrant" with "non-citizen", having the effect of removing all restrictions on entry by Australian citizens from the external territories such as the Cocos and Christmas Islands to the Australian mainland.

The Migration Legislation Amendment Act 1989 created a regime of administrative detention of "unlawful boat arrivals". Such detention was discretionary.

The Migration Reform Act 1992, which came into operation on 1 September 1994, adopted a mandatory detention policy obliging the government to detain all persons entering or being in the country without a valid visa, while their claim to remain in Australia is processed and security and health checks undertaken. Also at the same time the law was changed to permit indefinite detention, from the previous limit of 273 days. Mandatory detention has continued to be part of a campaign by successive Australian governments to stop people without a valid visa (typically asylum seekers) entering the country by boat. The policy has been varied since 1992 by the subsequent Howard, Rudd, Gillard, Abbott and Turnbull governments.