An affair between downtown moneyman Christopher O'Neill and his uptown girl -- the gorgeous Princess Madeleine of Sweden -- has become the hottest gossip of Stockholm's long, cold winter.
O'Neill, a 36-year-old millionaire who dispenses financial advice to super-wealthy clients, is "in a love affair" with his 28-year-old Swedish dish, a source close to the couple told The Post.
A Spanish tourist armed with a cellphone took a video of the lovebirds at the Central Park Boathouse that has become an Internet sensation in the Nordic nation. Madeleine, the height of style in a white fur vest, is seen affectionately rubbing O'Neill's arm.
"She is always happy when she is with him," the source said.
Madeleine, a k a the duchess of Hälsingland and Gästrikland, is the daughter of King Carl XVI Gustaf and Queen Silvia.
O'Neill's family also has a regal connection -- his mother, Eva, has dated Prince Charles, according the Swedish tabloid Aftonbladet.
While Madeleine's romance has flown under the radar here, pictures of O'Neill with gorgeous women -- in one 2008 photo he is seen posing with lingerie model Maryam Abdullina on a yacht -- appear occasionally on society Web sites.
O'Neill did not return phone calls, and no one answered the door at his East Village residence, where neighbors say they've spotted the couple canoodling.
Madeleine made headlines in April by calling off her wedding to lawyer Jonas Bergstrom after he reportedly cheated on her with a 21-year-old co-ed at a ski resort.
Afterward, the scorned royal moved to the Upper East Side.
She's since been linked to Paris Hilton's ex, Greek playboy Stavros Niarchos, and to a fellow Swede, Ranger goaltender Henrik Lundqvist.