Former conservative prime minister Malcolm Fraser, who came to power in 1975 after Australia's greatest constitutional crisis, died on Friday after a short illness at the age of 84, his office said.
His death came just five months after the demise of Gough Whitlam, the man Fraser replaced after the Labor figure became Australia's only prime minister to be sacked.
"It is with deep sadness that we inform you that after a brief illness John Malcolm Fraser died peacefully in the early hours of the morning of 20 March 2015," a statement said.
"We appreciate that this will be a shock to all who knew and loved him, but ask that the family be left in peace at this difficult time."
He leaves wife Tamie and four children.
Fraser, from Australia's conservative Liberal Party, began his term as the country's 22nd prime minister after the representative of Britain's Queen Elizabeth II, Sir John Kerr, dismissed Whitlam's government in November 1975 in a constitutional crisis.
He was appointed caretaker and despite persistent questions about the legitimacy of how he came to office, the man seen as a ruthless politician went on to win three elections, serving until 1983 and pursuing goals of reducing spending and responsible fiscal management.
He was also a strong supporter of human rights and helped shape Australian diplomatic and trade relations with East and Southeast Asia before being succeeded by Labor's Bob Hawke in 1983.
"The constitutional crisis of 1975 was one of the defining political events of our nation," said Prime Minister Tony Abbott.
"Malcolm Fraser held true to the belief that his actions were in the best interests of Australia. He was determined to 'turn on the lights' and restore Australia's economic fortunes.
"The greatest win in Australian political history confirms that he had correctly read the mood of the public.
"He was rightly proud of his government."
- Lasting legacy -
A staunch opponent of apartheid, Fraser was also noted for taking a strong stand in supporting reform in South Africa and playing a prominent part in the Commonwealth's efforts to establish an independent Zimbabwe.
He formed aid group CARE Australia, established the Australian Federal Police, enacted the nation's first Freedom of Information laws, and welcomed tens of thousands of Vietnamese boatpeople into the country.
Fraser continued to play a high-profile diplomatic role after leaving office, lobbying for Australia to have a permanent seat on the UN Security Council while serving on various Commonwealth observer groups overseeing elections in Pakistan, Tanzania and Bangladesh.
In 1988, Fraser was awarded the Companion of the Order of Australia and in 2000 was bestowed with Australia's Human Rights Medal for his contribution to the advancement of human rights, both at home and internationally.
In recent years, he had become an outspoken critic of the Liberal Party, speaking out particularly on indigenous issues, refugees and the war on Iraq, while being a prolific user of Twitter to share his opinions, tweeting more than 10,000 times.
His last tweet was on Wednesday: "Time for a new China vision - Asia and the Pacific", it said, regarding an event at the Australian National University.
Born into a wealthy family, he first entered parliament in 1955 and spent 10 years as a backbencher in the government of Robert Menzies.
He became Minister for the Army in 1966 under Harold Holt, and was also a minister in the governments of John Gorton and William McMahon.