Forrest and his wife Nicola are giving away a large portion of their multimillion-dollar wealth, with details to be announced at a ceremony in Canberra on Monday morning.
Mining magnate Andrew Forrest and his wife, Nicola Forrest, have made history today with a $400 million pledge the prime minister has called a "game changer".
He confirms the total amount is $400 million, the single largest donation by a living Australian.
"Despite so much of your achievement having been the result of your hard work, your determination and thus your just rewards for your efforts, you've nonetheless recognised that all good fortune comes with an element of fortune and that all of us, no matter how successful, know that if life's wheel had turned somewhat differently, we could be much less well off, much less well situated", Mr Turnbull told the gathering.
Mr Forrest, the founder of mining company Fortescue Metals, is estimated by Forbes to have a net worth of more than $5.5 billion.
"What an unbelievable thing Andrew Forrest is doing".
"Why this announcement matters in Australia is that it's the single largest philanthropic commitment in Australia from living donors, and it's part of the trend of more and bigger donations that we've seen in recent years", Davies said in a statement.
Fellow actor Jack Thompson said Mr Forrest's investment will bring more Australians together and eliminate the artificial divisions within the community.
Minderoo has supported more than 250 initiatives both within Australia and internationally, including fighting modern slavery, ending Indigenous disadvantage, and ensuring all children in Australia "thrive by five".
He also thanked his daughter Grace, who inspired the Walk Free Foundation, a charity working towards ceasing modern slavery.
"The immediate response was that's been done for tax and it had nothing to do with tax", Mr Forrest said.
Sarah Davies, chief executive of Philanthropy Australia, the country's peak body for philanthropy, said Australia did not have the United States' tradition of philanthropy which she described as the "gold standard".
He was Western Australia's finalist for Australian of the Year this year.