The world’s fourth-richest man, worth around $122bn, said he planned to hand over virtually all his financial assets to his charity foundation, starting with a donation of $20bn (£16.92bn).
“As I look to the future, I plan to give virtually all of my wealth to the foundation,” he tweeted.
“I will move down and eventually off of the list of the world’s richest people.”
The Microsoft co-founder is also the biggest philanthropist of all time, together with his former wife, Melinda.
The couple set up the foundation in their name in 2000 to tackle poverty, disease, and inequity around the world, particularly in developing nations, including funding vaccines. It is one of the world’s wealthiest philanthropic organisations.
Mr Gates announced the foundation now plans to increase its spending from nearly $6bn a year to $9bn by 2026.
“I have an obligation to return my resources to society in ways that have the greatest impact for reducing suffering and improving lives,” he added.
“And I hope others in positions of great wealth and privilege will step up in this moment too.”
The $20bn donation brings the Gateses’ lifetime irrevocable giving to $55bn, Forbes says.
It puts the couple ahead of their friend Warren Buffett, who has given away $48bn, most of it also to the Gates Foundation.
“Several huge global setbacks over the past few years have left many people discouraged and wondering whether the world is destined to get worse,” he wrote.
“The pandemic is one of the biggest setbacks in history. The war on Ukraine is a gigantic tragedy for the entire world.
“The damage from climate change is already worse than most models predicted. The US has taken a huge step backwards for gender equality and women’s health.”
But he said he was still optimistic.
“I believe it is possible to mitigate the damage and get back to the progress the world was making… the great crises of our time require all of us to do more.”
And he told Forbes: “I’ll get myself out of the highly visible part of the list with just, say, two more gifts of this magnitude. I would get myself off the top part of the list.
“Getting all the way off the list, that’s going to take me a while, but my direction of travel is clear.”
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