American media mogul Oprah Winfrey has achieved another milestone.

Her fortune hit a record US$4 billion on Monday to make her the first black female entrepreneur on the Bloomberg Billionaires Index – a ranking of the world’s 500 richest people. She is ranked at 494, just behind Mark Cuban and Ross Perot.

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Winfrey, 64, can largely thank the performance of Weight Watchers International for this latest marker.

Her fortune has increased by US$427 million this year as the company’s share price has more than doubled.

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The weight-loss company has mounted a comeback since 2015, when she bought a stake and agreed to pitch the brand.

The bulk of her fortune comes from ownership of the The Oprah Winfrey Show, which had a 25-year run.

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The founder of her own cable network, Winfrey just announced a partnership with Apple to produce original programmes and content.

Her inclusion brings the total number of women on the list to 65 and the number of female entrepreneurs to six.

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