The Sustainable Australia Party (SAP), officially registered as Sustainable Australia Party – Universal Basic Income, is an Australian political party that was formed in 2010.

The party has been registered federally since 2010. It was previously named the Sustainable Population Party and later the Sustainable Australia Party – Stop Overdevelopment / Corruption, before adopting its current name. In 2016 it also registered in the Australian Capital Territory, and contested the 2016 Australian Capital Election. In 2018 it also registered in Victoria for the 2018 state election and NSW for the 2019 state election.

In 2010 the party opposed Kevin Rudd's support for a "big Australia", saying that a large population would be "disastrous", is "way beyond [Australia's] long-term carrying capacity", and that "population growth is not inevitable". The party claims that "'stable population' policies would mean a more sustainable 26 million at 2050, not the Labor/Liberal 'big Australia' plan for 36 million and rising."

Sustainable Australia used to be called the Sustainable Population Party. Its current name was registered with the Australian Electoral Commission on 18 January 2016. The party missed out on registration for the 2010 federal election by several days, but leader William Bourke ran unsuccessfully for the Senate in New South Wales on an independent ticket with poet Mark O'Connor. The party was registered shortly after the election, on 23 September 2010.

The party was registered as "Stable Population Party of Australia", but on 28 February 2014 the Australian Electoral Commission approved a name-change to the "Sustainable Population Party". On 19 January 2016, the AEC approved a further name change to "#Sustainable Australia" (including a hash symbol).

The party ran at least two Senate candidates in every state and territory in the 2013 Australian federal election and many local candidates also. Timothy Lawrence was the candidate for Australian Stable Population Party in the 2014 Griffith by-election, arising from the resignation of Kevin Rudd. Lawrence received 666 votes, 0.86% of the primary vote. The party also contested the April 2014 re-run in Western Australia of the 2013 federal Senate elections. The party endorsed Angela Smith, an environmental scientist and a local candidate, for the 2015 Canning by-election. In September 2015 the party campaigned on a number of issues including education, paid jobs, infrastructure, health care, renewable energy and housing affordability.

In the 2015 North Sydney by-election its candidate and founder William Bourke received 2,189 votes, representing 2.88% of the primary votes.

The party has been involved in a preference harvesting scheme organised by Glenn Druery's Minor Party Alliance.