Murdoch divorces third wife Wendi Deng

News Corp chief Rupert Murdoch has filed for the divorce of his third wife Wendi Deng, citing an "irretrievably" broken marriage to a woman 38 years his junior.

The 82-year-old media tycoon's Chinese-born wife is perhaps best known for a 2011 incident when she leapt to defend her husband by striking a pie-wielding protester, prompting headlines calling her a "tiger wife".

After months of rumours and denials that the marriage was on the rocks, Murdoch on Thursday filed for divorce in the New York Supreme Court.

"I can confirm for the record that Rupert filed in New York State Supreme Court this morning for divorce," his spokesman Steven Rubenstein told AFP.

The filing stated the "relationship between husband and wife has broken down irretrievably".

A source close to News Corp said the couple had a pre-nuptial agreement but did not elaborate.

The divorce will not affect the way in which the media empire is run as Deng does not have stock or voting rights in News Corp, the source said on condition of anonymity

Murdoch's four oldest children, from previous marriages, have voting rights, the source said.

News of the impending divorce was not seen as a sign of problems at the company, and shares in News Corp rose 2.39 per cent on Thursday to close at $31.68.

Murdoch and Ms Deng, 44, married 14 years ago on the mogul's 50m yacht, the Morning Glory, in New York Harbour and the couple have two daughters, 11-year-old Grace, and nine-year-old Chloe.

Deng met Murdoch while working at his Star Television company in Hong Kong, where former colleagues have described her as an expert networker with big ambitions.

Born in the eastern Chinese city of Xuzhou in 1968 - at the height of the Cultural Revolution - she left China at 19 to study in the United States. She graduated from the Yale School of Management in 1996.

It is Murdoch's third failed marriage, with little time between divorces.

He divorced his first wife, Patricia Booker, with whom he had a daughter, in 1967 after 11 years of marriage. The same year he married Anna Maria Torv.

They were together for 31 years before their 1999 divorce.

The same year, Murdoch married Ms Deng.

Murdoch has built a $US60 billion global media empire, and, ironically, earlier this week the company's shareholders voted to split the business into two publicly traded companies.

21st Century Fox will hold the TV and movie interests, while News Corp will hold the newspaper and publishing assets. Murdoch will remain in charge of both companies after the split, as chairman and chief executive.

His youngest son James, 40, is believed to be the heir apparent to the family empire.

James was named News Corp's deputy chief operating officer in March 2011 and serves as chief executive of the news and entertainment giant's international operations.

Ms Deng became a YouTube sensation in 2011 when she was sitting behind Murdoch as he testified before a British parliamentary committee after the UK phone hacking scandal.

As assailant Jonathan May-Bowles approached with a pie aimed at her husband, Ms Deng, a former volleyball player, jumped to her feet and launched her right hand at May-Bowles.

While a News Corp spokesperson said the divorce would have no impact on the company, Murdoch's second wife Anna, who had daughter Elisabeth and sons Lachlan and James with Murdoch, reportedly pocketed $US1.7 billion in the divorce, including $US110 million in cash.

Murdoch's personal worth is estimated at $US8 billion.

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