At the castle of the countess Mariza
At the terrace of a castle with an adjacent park. Countess Mariza spends a long time of her life in the city, so she trusts her rural estate to her bailiff - Count Tassilo, who is operating under the name of Török. Tassilo hopes to earn a dowry for his sister Lisa - she doesn't know about the impoverishment of the family. He rather likes his service: he has never seen his mistress, just sends her the rents, and the servants and peasants treat him well. But this idyll is to come to an end: prince Populescu, an old Don Juan, comes and announces that countess Mariza will follow to celebrate her engagement there. Suddenly, she appears: A gorgeous, lively, but also a capricious young woman, who wants to disclose and celebrate the engagement with Baron Kolomán Zsupán. All guests have already arrived, but the engagement is only a fake, she secretly confesses to a friend, to get rid of her admirers.
She invented a fiancee to herself, based on the recollection of Strauss' operetta, "The Gypsy Baron". She announces that he was delayed by some business, and the engagement party will go on without him. But then, suddenly, he appears! Baron Zhupan read about his own "engagement" in the papers, and decided to come. He meets Mariza and they sing a duet together, "Do not laugh, Mariza, but marry I should". Mariza introduces her "fiancee" to the guests and they all go out to the park. There they surprise sad Tassilio, who sings an aria "In the spring stillness a gypsy sings afar", which he ends with a czardas. Both Mariza and the guests see it, and Mariza orders him to repeat it. He refuses, and the angry countess announces, that he is fired.
The guests are leaving the estate to go to the town, and get dissipated in cabarets. Maritza meets a young gypsy Manja who predicts that she will be very happy in love. "One moon will pass over this Earth and Mariza will find her happiness", she sings. Mariza refuses to go and stays on her estate. She stops Tassilio from leaving and apologises. She repeats the refrain of his aria "Hey, gypsy", and their duet ends Act I.
Scene 1: Mariza's estate park
Visitors came to visit Mariza. Lisa, Tassilo's sister, who does not know that he is a manager here, and Zsupan, who came to visit his "fiancee". They like each other and Zhupan repeats twenty times that if he didn't love Mariza, he would have dreamed about Liza tonight. Tassilo is surprised and happy to meet his sister. In a duet "Come here and sit down", they recollect their childhood.
Scene 2: A parlour in Mariza's house
A month of her solitude has passed; guests are coming. They make fun of Tassilo. He writes a letter to his friend, to tell him that he endures a lot, but Lisa is his only close relative, and he will endure everything for her dowry. He stops writing it abruptly when Mariza comes in. Together, they sing a duet, a confession of love ("My tender friend!") Populescu tells Mariza that he saw her manager in the park with a pretty girl, and he finds the unfinished letter where Tassilo speaks about a dowry. Mariza does not know that Tassilo has a sister, so she sees him as a dowry-hunter. The finale of the Second act is a dramatic scene with an aria "Hey, Mariza, be calm, hey, Mariza, endure this pain", chaffing of the guests, perplexed Tassilo... Mariza humiliates and insults him, and throws him out. Lisa comes, runs towards her brother, and they leave together. Mariza understands that she's made a mistake.
The next morning Zsupan proposes to Lisa in the park. They sing a merry duet together "A lad loved a lass". An old aunt of Tassilo arrives, who announces that she has bought back Tassilo's estate from his debtors and left it to him. Tassilo comes to Mariza to report the estate conditions. They reconcile. Two couples end the operetta by singing together "Time passes but love does not wait."