Ken Griffin & Anne Dias Griffin: The Billionaire Hedge Fund Divorce That Put Prenups on Trial
Two hedge fund billionaires went to war over a prenup, three kids, and a $9 billion fortune
Key Facts
What Happened
Ken Griffin, founder of Citadel LLC and Illinois' richest person with a fortune exceeding $9 billion, filed for divorce from Anne Dias Griffin in July 2014. What made this divorce extraordinary was that both spouses were hedge fund managers -- Anne ran her own fund, Aragon Global Management -- making this a rare battle between two financial titans. The couple had three children, all under seven years old, and the central fight was over their prenuptial agreement and whether Anne could relocate the children to New York.
Anne challenged the validity of the 2003 prenuptial agreement, arguing she signed it under duress. According to filings, the prenup would have entitled her to roughly 1% of Griffin's fortune -- approximately $22.5 million in a guaranteed settlement sum, regardless of the marriage's length. Anne wanted the prenup thrown out, which would have opened the door to a far larger share of the marital estate under Illinois' equitable distribution laws. Ken fought to enforce it, while Anne simultaneously sought primary custody and permission to move the children to New York.
The case became the most expensive divorce proceeding in Illinois history, with both sides deploying armies of lawyers and private investigators. Custody evaluations, psychological assessments, and forensic accounting consumed over a year. The trial was set to begin on October 6, 2015 -- but on October 7, the couple announced a surprise settlement. Anne agreed to joint custody and withdrew her New York relocation petition. The financial terms were sealed, but the prenup's core framework was reportedly preserved.
The Griffin divorce became a landmark case for prenuptial agreement enforcement. Anne's legal team threw everything at the prenup -- duress claims, arguments about changed circumstances, allegations of inadequate disclosure -- and yet the agreement held. For anyone entering a marriage with significant assets, this case underscores both the power and the limits of prenuptial protection.
Legal Breakdown: Prenuptial Agreements
Challenging a Prenuptial Agreement
Anne Dias Griffin's attempt to invalidate the prenup tested the most common grounds for prenup challenges: duress at signing, inadequate financial disclosure, and unconscionability. Illinois courts apply a rigorous standard -- the challenging party must prove the agreement was involuntary or fundamentally unfair at the time of signing. Anne's failure to overturn the prenup, despite having elite legal representation, demonstrates how difficult it is to void a properly executed prenuptial agreement.
Custody Battles in High-Net-Worth Divorces
The custody fight was just as intense as the financial one. Anne sought primary custody and permission to relocate the children to New York, while Ken wanted them to remain in Chicago. Illinois requires the relocating parent to prove the move serves the children's best interests -- a high bar when the other parent has deep community ties. The final agreement for joint custody in Chicago reflects the courts' reluctance to separate children from either parent's home base.
Privacy in Billionaire Divorce Proceedings
Both parties fought to seal records and limit public disclosure, but the sheer scale of the case attracted relentless media attention. Financial details leaked through filings, and the custody battle played out in public court. For ultra-high-net-worth individuals, the Griffin case illustrates that even the most aggressive privacy efforts cannot fully shield a divorce from public scrutiny once it enters the court system.
What This Means for Your Divorce
- →A well-drafted prenuptial agreement signed with independent counsel is extremely difficult to overturn, even in a multi-billion-dollar divorce.
- →When both spouses are high earners, the financial dynamics shift -- but the prenup still controls the outcome if it was properly executed.
- →Custody relocation requests face a steep burden of proof. Courts prioritize stability for young children over a parent's preference to move.
- →Settling on the eve of trial is common in high-net-worth cases -- the risk of public disclosure often forces both sides to compromise.
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This article is based on publicly available court records, news reports, and legal analysis. It is provided for educational purposes only and does not constitute legal advice. No attorney-client relationship is created by reading this content.
Divorce laws vary by jurisdiction. Always consult a licensed attorney in your area before making legal decisions.