Billionaire George Soros’s son Robert and his estranged wife Melissa Schiff are at risk of forfeiting their entire art collection — including pieces by Jeff Koons and Christopher Wool — if they can’t agree on its value, his lawyer said.

The former couple were in Manhattan Supreme Court Wednesday for the opening day of their $350 million divorce trial.

Soros’ attorney, Alan Feigenbaum, said their prenuptial agreement states that if “the parties cannot agree on a value…property should be sold.”

But Schiff’s lawyer, Bernard Clair, disputed that interpretation. He argued that an appeals court ruled in April that “the prenup does not address the disposition of marital art.”

Soros, who until recently ran his father’s $28 billion investment management firm, wants to sell off their collection, while Schiff wants to keep selected pieces.

They’re also fighting over a $5.85 million Rhinebeck farm, which Schiff testified that she “loves more than anything.”

Soros filed for divorce from his wife of 22 years in 2014 — after an affair with a nude model.