Most expensive divorce in history? Harold Hamm oil tycoon could lose half of his $11.3 billion fortune

There’s divorce and then there’s billionaire divorce.

Harold Hamm, Oklahoma oil tycoon and Richest Person No. 35 on Forbes’ list of Richest Americans, could stand to lose over $5 billion of his estimated $11.3 billion fortune in the divorce settlement of his estranged second wife, Sue Ann Hamm.

Reuters speculates that if the couple failed to sign a prenuptial agreement before their 1988 wedding, theirs could swiftly escalate into the most expensive divorce of all time and would smash the previous settlement record holders Rupert and Anna Murdoch, whose marital dissolution cost the media mogul $1.7 billion of his fortune – a mere pittance in comparison to what Hamm could stand to lose.

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“I don’t know of anything that’s ever been this big. There’s just so much money involved,” Barbara Atwood, a professor emeritus of the University of Arizona, tells the news agency.

From a business perspective, this could also prove disastrous for the self-made billionaire. Hamm is the CEO of Continental Resources, a major player in the U.S. oil industry. Sue Ann has also “held key posts” at Continental although she has since left the company.

Under Oklahoma law, any wealth gathered during a marriage that is the result of efforts by both spouses could be subject to “equal distribution,” a factor that could threaten Hamm’s stake in the company.

“A court in Oklahoma may look closely at what each party has contributed,” said legal specialist Atwood. “But it sounds to me like both spouses here were working hard in the business.”

Continental stocks have also taken a hit since Hamm confirmed the divorce proceedings, says Forbes.

Last year, Sue Ann filed for divorce, alleging that her husband was having an affair that she discovered back in 2010. The couple has two adult children.

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To put their split in perspective, Business Insider has compiled a list of the most expensive divorces of all time.

In addition to the $1.2 billion Murdoch divorce in 1999, Formula One CEO Bernie Ecclestone paid out $1-1.2 billion to his ex-wife Slavica in 2008; Saudi arms dealer and businessman Adnan Khashoggi handed over $874 million back in 1974 to ex-wife Soraya; the Craig and Wendy McCaw divorce cost him $460 million, while Mel Gibson’s infidelities cost the actor/director $425 million when his ex-wife Robyn finally had enough.

But all the settlements on this list combined still don’t add up to the potential payout in the Hamm divorce.