Billionaire real estate developer Stephen M. Ross, the man behind New York’s Hudson Yards and the owner of the Miami Dolphins, is embroiled in an $8 billion divorce with his jewelry designer wife of 18 years, Kara.

Page Six has exclusively learned the Related Companies founder — who’s also an investor in Equinox and SoulCycle — and wife Kara have separated and are currently quietly negotiating a divorce.

Sources close to Ross — a longtime friend of Donald Trump who caused a furor by throwing a $100K-a-seat fundraiser for the then-president in the Hamptons in 2019 — insist the split is amicable.

Ross, 80, is said to be worth between $7 billion and $8 billion, but we are told there is a pre-nuptial agreement between the couple, who married in 2003.

The former couple confirmed their split in a joint statement to Page Six: “We have deep love and respect for each other. We will continue to be a part of each other’s lives and support what is best for the health and happiness of our family.” They each have two children from previous marriages.

Sources say that while the pair has not yet formally filed any divorce papers, they have both hired prominent New York divorce attorneys.

Stephen is being represented by William D. Zabel from Schulte Roth & Zabel, whose famous clients have included billionaire George Soros, golfer Greg Norman and Howard Stern. Kara is represented by Judith Poller at Pryor Cashman, who has previously handled cases for Drew Barrymore and Scarlett Johansson.

A legal source not involved in the Ross case speculated the divorce settlement Kara could win “could likely start at $100 million and go north to $200 or $300 million — making this one of the most expensive divorces in New York.”

Another insider said that while Kara would get a sizeable settlement, Stephen’s ownership of the Miami Dolphins and Related Companies would not be split.

The insider said, “His business holdings will not be affected by the divorce.”

Stephen started out as a tax attorney before founding Related Companies in 1972, and their Hudson Yards development on Manhattan’s West Side opened in March 2019. Related is said to have developed or acquired more than $60 billion worth of properties from California to Shanghai, including a large amount of affordable housing.

Ross acquired 95 percent of the NFL’s Miami Dolphins for more than $1 billion in 2008 and 2009.

Kara Ross, née Gaffney, 54, is a jewelry designer to stars including Michelle Obama, Oprah Winfrey and Anne Hathaway

Naturally, the couple has an impressive real estate portfolio. They share a penthouse at Related’s Time Warner Center overlooking Central Park that was featured in Architectural Digest in 2015. The penthouse boasts a 42-foot-long living room, marble floors, a massive art collection, and five bedrooms.

The couple announced in 2019 they were selling the property and were planning on moving to Hudson Yards, but as of today, the penthouse is still on the market for $62.5 million.

There’s also a 10,000-square-foot mansion in Southampton and their Palm Beach, Fla., oceanfront mansion, known as “The Reef,” an architectural gem for which Ross reportedly paid $31.8 million in 2008.

Meanwhile, Stephen is focusing on New York’s mayoral race and is raising “tens of millions of dollars” to get New Yorkers to vote in the upcoming Democratic primary.

He recently invited New York business leaders to a March 15 lunch meeting to discuss what he called the “most important election of our lifetime and in NYC’s history.”

Ross said the winner of the June Democratic primary will “decide if NYC will rebound or languish” and that he is forming a committee to raise money for a large effort to drive voter turnout.

New York’s business leaders want to elect a moderate mayor to lead the pandemic recovery after feeling shunned by Bill de Blasio, who will leave office after two terms.