Texas billionaire Sid Bass abruptly dumped his longtime partner for another woman after allegedly promising to provide for her for life — the latest in what her lawyers portray as a decades-long pattern of the oil heir replacing wives and lovers with new flames already waiting in the wings.
Oona Sperr, a New York interior designer who says she spent more than 10 years living with the 84-year-old Bass, is demanding at least $400 million in a bombshell federal lawsuit accusing him of reneging on promises of lifelong financial security and interests in their lavish homes.
The complaint, filed Monday in Manhattan federal court, portrays Sperr’s breakup as the latest chapter in what her lawyers call Bass’s history of “marriages, divorces, and repeated infidelities.”
“Just as Sid had done to [his first wife] Anne [Hendricks Bass], he left his marriage to [second wife] Mercedes [Tavacoli Kellogg Bass] with another relationship already established,” the suit alleges.
Sperr claims her decade-long partnership with Bass began in earnest in January 2014 with an invitation that would prove bitterly ironic.
Over lunch at his Manhattan townhouse, Bass allegedly asked her: “How about you never leave?”
Sperr says she abandoned her interior design career to manage Bass’s households and accompany him around the world in return for promises of financial support and shared ownership of property they acquired.
For more than a decade, they lived in what Sperr dubbed “Bass Land” — a rarefied world that included Manhattan mansions, a sprawling Colorado ranch, a private Gulfstream jet and the Bass family’s 21-mile-long private island off the Texas coast, according to the complaint.
Bass allegedly referred to Sperr as “Mrs. Bass” while traveling, bought her a 25-carat diamond for $2.1 million sized for her left ring finger and later gave her a 20-carat emerald for $1 million — the same type of gemstone he allegedly noted he had given each of his previous wives.
But over breakfast at their Pagosa Springs, Colo., home on Sept. 3, 2024, Bass allegedly delivered a dramatically different message.
“I want a separation. You are to pack and leave,” Bass allegedly told her.
Sperr claims Bass initially offered her $50 million, a Manhattan home, another property, continued help from his staff and care for her elderly mother.
When Sperr asked whether another woman was involved, Bass “vehemently denied it,” according to the suit.
Weeks later, while packing in Colorado, Sperr claims she overheard Bass speaking to art adviser Althea Viafora Kress on his headphones, calling her “sweetheart” and exclaiming: “You’re my gal!”
She allegedly heard them discussing Viafora Kress moving into the Colorado home days after her departure.
The complaint claims Viafora Kress demanded that Sperr’s possessions be removed, that Bass stop speaking directly to her and that he not drive her to the airport.
Bass nevertheless drove Sperr to the airport on Sept. 30, 2024 — the couple’s last day together, according to the suit.
The saga took another bizarre turn the following year.
Sperr says she received a six-sentence email titled “News” from Bass’s account on Aug. 22, 2025, announcing that he had married Viafora Kress on Aug. 9 at the Bass family’s San José Island compound.
But Sperr alleges Bass neither wrote nor sent it.
Instead, she claims Viafora Kress “used Sid’s account to announce her own purported marriage to him.”
The complaint goes so far as to call the nuptials a “coerced ceremony” and “sham marriage ceremony,” alleging that Viafora Kress increasingly isolated Bass from longtime friends and employees and exerted control over his communications, household and spending.
The suit alleges Bass had suffered at least three mini-strokes and that a doctor told him and Sperr in 2019 that a brain scan showed abnormalities consistent with a “particularly pernicious form of Parkinson’s disease.”
Sperr also alleges Bass’s drinking increased during the pandemic to as much as two bottles of wine on most days as she observed changes in his judgment, temperament and memory.
The complaint reaches decades into Bass’s romantic history to support its claims of a pattern of infidelity.
His first marriage to Anne unraveled amid his relationship with Mercedes in the 1980s, when both Bass and Mercedes were married to other people, according to the filing.
Sperr claims Bass later told her that by the time his divorce from Anne was nearing completion, he no longer wanted to marry Mercedes but felt unable to back out because he had caused her divorce.
In one of the suit’s most extraordinary allegations, Sperr claims Bass told her that during his divorce from Anne “he had paid Anne’s psychiatrist to inform Sid about Anne’s sessions.” Anne died in 2020.
Bass married Mercedes in 1988, but Sperr alleges he later had a secret relationship with another married woman, Patricia Zohn Pfeiffer.
The complaint claims Pfeiffer subsequently stalked Bass and Sperr around the Upper East Side and that Bass eventually presented her with agreements designed in part to “secure her silence regarding the affair.”
Sperr also alleges Bass bragged about “how brilliantly he manipulated Mercedes through their divorce” by maintaining their life together while promising a future friendship he allegedly had no intention of keeping.
Bass eventually retreated even from the $50 million breakup package he initially offered Sperr, according to the complaint.
A proposed “Maintenance Agreement” instead offered $5 million annually for 10 years, tenancy rather than ownership of a Manhattan home and fewer of the other benefits Sperr claims Bass had promised.
Sperr sued Bass for breach of an alleged oral agreement and other claims and Viafora Kress for alleged tortious interference, among other claims.
“This is a case about broken promises,” Robbie Kaplan, Sperr’s attorney, told The Post in a statement.
“Sid Bass is a billionaire at least four times over. Oona is the woman who spent a decade making Sid’s life convenient — abandoning her career, managing their shared homes and affairs, caring for him through his serious illnesses — all because Sid agreed that he would take care of her and her 96-year-old mother no matter what.
“After accepting all the benefits, Sid abruptly ejected Oona, breaking his promises to her,” Kaplan added.
“Because Sid has failed to keep his word, Oona, now 64 years old, had no choice but to bring this case.”
The Post has sought comment from Bass, Pfeiffer and Viafora Kress.
