Amazon chief Jeff Bezos is putting $2bn (£1.5bn) into a charitable fund he has established to help the homeless and set up a new network of schools.
The world's richest man announced the move in a tweet, saying the charity would be called the Day One Fund.
Mr Bezos - reportedly worth more than $164bn - has faced criticism for not doing more philanthropic work.
And US Senator Bernie Sanders has criticised working conditions in Amazon warehouses.
Mr Bezos asked on Twitter last year for suggestions on how he might use his personal fortune, which this year has soared due to Amazon's surging share price and US tax cuts.
He said on Thursday that the "Bezos Day One Fund" will contribute to "existing nonprofits that help homeless families" and also fund "a network of new, nonprofit, tier-one preschools in low-income communities".
The fund will be split between Day 1 Families Fund and Day 1 Academies Fund.