The money would finance work by scientists, activists and other groups.
Writing on his Instagram account, Mr Bezos said it will begin issuing of grant this summer.
Amazon has an estimated net worth of more than $130bn, so the pledge represents almost 8% of his fortune. Compared to some multi-billionaires,
Jeff Bezos had done only limited philanthropy.
His biggest donation before Monday’s pledge is thought to have been $2bn in September 2018 to help homeless families and fund schools.