The shortfall will have meant hundreds of thousands of preventable deaths across much of the developed world, with millions more likely to die as a result.
The United States, which shut down USAID as one of the first acts of Donald Trump's second presidency, was responsible for for three quarters of the decline alone.
Multi-billion dollar cuts by other major donors - the UK (down 11 per cent), Japan (5.6 per cent) and France (10.9 per cent) - have exacerbated the global crisis in development assistance.
The US retreat from supporting the world's poorest and most in-need populations meant that for the first time, Germany was the top foreign aid provider last year in real terms.
Germany's development assistance hit A$41b in 2025, ahead of the United States by almost $A200m.
In terms of percentage of a country's national income - or GNI - Norway was the most generous, giving 1.03 per cent.
Australia, by contrast, is of below-average kindness, ranking 25th of 32 donor nations, giving 0.18 per cent of GNI, behind the UK (0.43 per cent) and New Zealand (0.27 per cent).
Wealthy countries, including Australia, have signed up to a United Nations goal of giving 0.7 per cent of GNI - or seventy cents in every $100 from each nation's budgets - to lesser developed nations.
Just four nations did so in 2025: Norway, Luxembourg, Sweden and Denmark, with an average of 0.26 per cent.
Oxfam Australia said the figures should spur Australia to step up its global giving to fill gaps left by others, helping to combat diseases like HIV-Aids and malaria.
"Oxfam analysis found that global aid cuts mean a child under 5 could die every 40 seconds by 2030. If this trend continues, aid cuts could kill over 9 million people by 2030," head of humanitarian Lucia Goldsmith said.
"The governments of wealthy nations are turning their backs on the lives of millions of women, men and children in the Global South through severe aid cuts."
Oxfam research from January found a child under five years old could die every forty seconds due to the US aid cuts.
Another study published by global health publication Lancet last year suggested aid cuts - at 21 per cent - would kill almost 700,000 people last year, and cumulatively 9.4 million people by the decade's end.
Australia's Department of Foreign Affairs and Trade has budgeted $5.1 billion in official development assistance this financial year, with a small increase in line with inflation.
Foreign Minister Penny Wong's office has been contacted for comment.
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