Traditionally, the classic definition of marriage dates back to that given by Lord Penzance in Hyde v Hyde & Woodmansee [1861–73] All ER Rep 175 as “the voluntary union for life of one man and one woman to the exclusion of all others.”

So in Australia at present there are four conditions for a marriage:

• the marriage must be voluntary;

• the marriage must be for life, ie the parties' intention at the time of the marriage;

• the union must be heterosexual; and

• the union must be monogamous.

Pursuant to s 51(xxi) of the Commonwealth of Australia Constitution Act, the Commonwealth Government in Australia has power to make laws relating to marriage, and by implication, the breakdown of those marriages. The constitutional validity of the Commonwealth Government to make such laws is no longer in dispute.

However, the delegation of powers to the Commonwealth in the Constitution does not extend to the power to make laws in respect of de facto (including same sex) relationships. That power resided with the individual state or territory governments until the governments of all states and territories, other than Western Australia, referred those powers to the Commonwealth, leading to the changes in the Family Law Act 1975 that were comprised in the new Pt VIIIAB, inserted into the Act in 2009, extending the operation of the Family Law Act to de facto relationships.

Marriage is regulated in Australia primarily by the Marriage Act 1961 (Cth) which makes statutory provision for the entry into a valid marriage and in respect of the recognition of foreign marriages. The Family Law Act then regulates the ending of marriages by divorce or decrees of nullity and consequent arrangements for children, financial support and property of the marriage.

The Family Law Act was amended again in 2009 to add, after a referral of powers from the participating states and territories, jurisdiction over the breakdown of de facto relationships (defined to include same sex relationships).

The formalities for a valid marriage ceremony in Australia are set out in the Marriage Act 1961 and the regulations made pursuant to that Act. See Valid marriages. In the event the formalities are not met, then the marriage may be declared to be a nullity.

Part VA of the Marriage Act 1961 sets out the statutory provisions that relate to the recognition of foreign marriages and divorces. See Overseas marriage.