The wealthy widow Hanna Glawari is in Paris, looking for a new husband. Baron Zeta, the ambassador of her homeland, Pontevedro, is scheming to ensure she marries one of her countrymen in order to save Pontevedro from bankruptcy. The man he has in mind is Danilo Danilovitsch, but it soon turns out that the two were former lovers. Danilo’s is too proud and will not marry Hanna for her wealth. But he does agree to sabotage the efforts of the other bachelors at a party that evening.
The next day, Hanna hosts a party at her Parisian Villa in celebration of the Grand Duke’s birthday. During the festivities, Hanna announces her engagement to the French bachelor Camille. Baron Zeta is distraught and Danilo suddenly aware of his true feelings for Hanna, storms out to go and drown his sorrows at Maxim’s, his favourite cabaret club. Hanna sees Danilo’s reaction and realises that he does indeed love her and rejoices.
Hanna follows Danilo to Maxim’s and reveals to him that the engagement to Camille was a ruse; she was simply protecting another woman’s reputation. Danilo is delighted but still will not propose to Hanna. She then reveals that her late husband’s will states that she will lose her fortune if she remarries. Whilst all the other bachelors lose interest, Danilo is free to propose with his pride intact. She accepts and reveals a final twist, if she were to marry she would lose her fortune…to her new husband.