MacKenzie Bezos, the ex-wife of Amazon boss Jeff Bezos, has promised to give half her fortune to charity.
She joins billionaires such as investor Warren Buffett and Microsoft founder Bill Gates in the Giving Pledge.
The pledge was started by Buffett and Gates and calls for the richest to give away half or more of their wealth.
Bezos is estimated to be worth almost $37bn. She and Mr Bezos divorced earlier this year.
She acquired 4% of the company in the settlement.