Also on Thursday, Bezos said he will commit $2 billion to helping homeless families and starting pre-schools for low-income communities. The first will fund existing nonprofits and issue annual awards to organizations doing "compassionate, needle-moving work" to shelter and support the immediate needs of young families.
The second will launch a network of "high-quality, full-scholarship" preschools in low-income communities, which a Day One Fund organization will directly operate.
Bezos made the announcement on Twitter a year after asking for ideas on how he could use his personal fortune - now estimated at more than $160 billion - for charitable efforts. "The media is going to be fine", Bezos said, according to AFP, before paraphrasing Post editor Marty Baron: "The administration may be at war with us, but we are not at war with the administration".
In his Instagram post Jeff Bezos said "Amazonians" were wearing pyjamas to work "across the globe" to raise awareness of childhood cancer.
But in the world of ultra-rich tech philanthropists, it's roughly on par with other do-gooding efforts.
"We're hoping that local, state and federal governments see this as a call to invest more in preschool and childcare", he said.
However, he has recently said he is looking to use his wealth for philanthropy, following in the footsteps of Bill Gates and Mark Zuckerberg.
The $2bn also falls short of the "giving pledge" initiative launched by Mr Gates and billionaire investor Warren Buffett, who have encouraged wealthy individuals to pledge half their fortunes for philanthropy.
He also operates the private space exploration firm Blue Origin and owns The Washington Post newspaper. In January, Bezos also personally gave $33 million USA in college scholarships for young immigrants living in the U.S. illegally.
The staggering fortunes of the likes of Bezos, Gates and Facebook CEO Mark Zuckerberg have created a second Gilded Age in the U.S. and "a new generation of megagivers", Callahan said.
He said he did not know how much money he would eventually give away.
The Amazon chief's wealth has become problematic for some. "It was a Day 1 outlook that made me reach out to ask for suggestions on approaches to philanthropy previous year". "What the president should say is, 'This is right, I'm glad I'm being scrutinised.' That would be so secure and confident".