- For her daughter, see Marie Kalergi (1840-1877).
At the age of seventeen Maria Nesselrode married Jan Kalergis, a rich landowner, who was much older and proved to be of a jealous disposition. Though they had a daughter, Marie, born in 1840 in Saint Petersburg, less than a year after their wedding they mutually decided to separate. Despite several attempts to overcome their aversion for each other, they would continue living separately, without divorcing, until Jan's death. He ensured Maria a prosperous life; to be sure, after their separation the division of their assets was in dispute, but they did allow her to tour Europe, including Saint Petersburg, Warsaw, Paris and Baden-Baden.
The course of Maria's marriage may have been influenced by her childhood experiences. A year after her birth, her father, Fryderyk Karol Nesselrode (of German descent) and his wife Tekla Nałęcz-Górska (of Polish descent), had separated due to personality differences. From her sixth year, Maria had been reared in Saint Petersburg in the home of her paternal uncle, Karl Robert Nesselrode, a Russian diplomat of German descent who for forty years (1816–56) was the Tsar's minister of foreign affairs and who saw to it that Maria received a thorough education.
She may have inherited her musical talent from her parents, and for a while took lessons from Chopin, who praised her talent. She was taught Polish by her mother and also spoke French (then the language of Polish salons), German, English, Italian and Russian.
She is remembered as the great love of Cyprian Norwid. For her, the acquaintance with the young poet was but one of many episodes in an active social life. He, shy and deferential, withdrew into the shade of the beautiful Maria's other admirers. For many years he harbored feelings for her that more than once served him as a source of poetic inspiration. He confided his feelings in letters to Maria Trembicka (General Stanisław Tręmbicki's daughter who later married a man named Faleński), a close friend of the "white siren." Encouraged by his confidante's friendship, he proposed to Maria Kalergis but was not accepted.
From 1847 she lived in Paris, then from 1857 in Warsaw. Guests at her salons included Liszt, Richard Wagner (who dedicated Tristan und Isolde to her), de Musset, Moniuszko, Gautier, Heine (who dedicated his poem "The White Elephant" to her) and Chopin. Back in Warsaw she became a patroness of the arts and took part in charity fund-raising concerts and theatrical performances. Her resources were always available to those in need.
When Stanisław Moniuszko wanted to premiere the four-act version of his opera Halka in Warsaw, he was opposed by the director of the Warsaw government theaters, Siergiej Muchanow (who was also the Warsaw chief of police and in 1863 would become Maria's second husband). Thanks to Maria's intervention, Moniuszko managed to get the opera put on. Three months after the January 1858 opening, she organized a concert to benefit Moniuszko, who was having financial difficulties. The concert raised 25,000 Polish złotych, which enabled the composer to meet his basic needs and take a journey abroad.
Maria Kalergis had an appreciable influence on the development of musical culture, helping found the Warsaw Musical Institute (now the Warsaw Conservatory) and founding with Moniuszko the Warsaw Musical Society, now the Warsaw Philharmonic. In 1857–71 she frequently appeared as a pianist.
Soon after her husband's death in 1863, she married Siergiej Muchanow, ten years her junior. He was with her during her illness and nursed her devotedly through her final days. It was probably then that, sensing the approaching end of her life, Maria destroyed her correspondence. Her letters to her daughter, son-in-law and friends have survived, however, and have made it possible to reconstruct many facts about her life and are a valuable source of knowledge about the period. She was interred at Warsaw's Powązki Cemetery. On her death, Liszt wrote his Elegy on Marie Kalergi.
Maria Kalergis' grandson, Jan Henryk Maria Count Coudenhove, with Emperor Franz Josef's permission, changed his surname to Coudenhove-Calergi. He married a Japanese lady, Mitsuko Aoyama. Their son, Count Richard Coudenhove-Kalergi, in 1923 founded the Paneuropean Union.
- Maria Kalergis, Listy do Adama Potockiego (Letters to Adam Potocki), ed. by Halina Kenarowa, translated from the French by Halina Kenarowa and Róża Drojecka, Warsaw, 1986.
- Stanisław Szenic, Maria Kalergi, Warsaw, Państwowy Instytut Wydawniczy, 1963.
- Stanisław Szenic, Cmentarz Powązkowski 1851-1860 (The Powązki Cemetery, 1851–60), Warsaw, 1982.