"They are separated," a source close to the Real Housewives of New York City stars tells E! News.
We're told, however, that the split "literally happened within the last few days," despite Mario's other relationship (and months of tabloid speculation that he was cheating).
Word of the split comes just days after Ramona cohosted an event in Manhattan.
"She hosted the Ramona Singer Wine Dinner at David Burke at Bloomingdales the night of Jan. 23," a guest at the dinner tells E! News. "But she left early, before dessert was served. She left alone."