"If our own great grandchildren don't have lives better than ours, something has gone very wrong", Bezos said in a tweet on Thursday.
Bezos solicited ideas on Twitter a year ago for ways to donate some of his wealth.
He cited his work at his space company, Blue Origin, and his investment, estimated now at $1 billion a year, "in the future of our planet and civilization through the development of foundational space infrastructure".
Some resorted to the same argument as US President Donald Trump, who has attacked Amazon for not paying enough taxes and using US postal office as its "delivery boy".
Amazon founder Jeff Bezos is to launch a $2bn (£1.53bn) fund to help homeless families and launch pre-schools in poor communities.
Bezos, and Amazon, have been criticized in Seattle for not doing more to help the needy and have become focal points in the booming region's angry debate about traffic, housing prices and homelessness.
The new philanthropic effort is called the Bezos Day One Fund, a nod to the executive's management philosophy that organizations must view every day with the fervor of a new start, or face stagnation and decline. "The child will be the customer", he wrote in his post.
The Day 1 Academies Fund will launch and operate a network of high-quality, full-scholarship, Montessori-inspired preschools in underserved communities.
Many were eager to hear any hint of where Bezos had made a decision to put Amazon's second headquarters, with multiple locations in the Washington region in contention.
Bezos hasn't said how much he'll be contributing to the fund in coming years.
Where a "network" of Bezos preschools is concerned, we should be especially sceptical.
"The customer is going to be the child", Bezos said. The most notable involving more than $40 million USA to the local nonprofit FareStart - a hospitality training program and restaurant business that aims to combat homelessness and poverty - and Mary's Place, whose mission to find and provide shelter for every child.
Bezos, with an estimated fortune of more than $160 billion, is now the world's wealthiest man, according to Forbes.
The so-called Day One Fund will be multi-billionaire businessman's most significant foray into philanthropy to date.
Many Twitter users agreed with that reasoning. "If billionaires like Bezos were properly taxed then we wouldn't need billionaires like Bezos to sweep in and "rescue" people failed by our underfunded systems," one wrote.