May 28 (Reuters) - MacKenzie Bezos, the former wife of Amazon.com Inc Chief Executive Jeff Bezos, pledged on Tuesday to give away half her fortune to charity, following a movement founded by billionaires Warren Buffett and Bill and Melinda Gates.

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 Berkshire Hathaway Inc's Buffett and Microsoft Corp 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," MacKenzie Bezos said in a statement. "My approach to philanthropy will continue to be thoughtful. It will take time and effort and care."

The fortune of Jeff Bezos was estimated by Forbes magazine to be $131 billion this year. Jeff and MacKenzie Bezos divorced earlier this year. (Reporting by Peter Szekely in New York; Editing by Scott Malone)