MacKenzie Bezos, the former wife of Amazon.com chief executive Jeff Bezos, pledged on Tuesday to give away half her fortune to charity.

Her announcement follows a movement founded by billionaires Warren Buffett and Bill and Melinda Gates.

At the time of the divorce settlement it was revealed MacKenzie Bezos would retain Amazon stock worth more than $35 billion (€31 billion) after her separation in what has been billed as the biggest divorce settlement ever.

Her 4 per cent stake in Amazon – a quarter of the couple’s collective holdings – ranked her the world’s third richest woman, after Françoise Bettencourt Meyers, the L’Oréal heiress, and Alice Walton, the daughter of Walmart founder Sam Walton, according to Forbes’s estimates of their net worth.

MacKenzie Bezos, whose former husband is the world’s richest man, was one of 19 people on Tuesday to sign the “Giving Pledge,” a campaign announced in 2010 by Mr Buffett of Berkshire Hathaway and Microsoft co-founder Bill Gates. It calls for the super-rich to give away more than half their fortunes during their lifetimes or in their wills.

“In addition to whatever assets life has nurtured in me, I have a disproportionate amount of money to share,” said MacKenzie Bezos. “My approach to philanthropy will continue to be thoughtful. It will take time and effort and care.”

Jeff Bezos’s fortune was estimated by Forbes magazine to be $131 billion (€117 billion) this year. Jeff and MacKenzie divorced earlier this year. – Agencies