Josephine Brunsvik or Countess Jozefina Brunszvik de Korompa (Hungarian: Brunszvik Jozefina; 28 March 1779 – 31 March 1821) was probably the most important woman in the life of Ludwig van Beethoven, as documented by at least 15 love letters he wrote her where he called her his "only beloved", being "eternally devoted" to her and "forever faithful”. Several musicologists consider her to be the most likely recipient of the mysterious "Letter to the Immortal Beloved".
Josephine Countess von Brunsvik was born on 28 March 1779 in Preßburg (now Bratislava in Slovakia), then part of the Kingdom of Hungary. Her father Anton died in 1792, leaving his wife Anna (née von Seeberg) with four young children; the other three were Therese (1775–1861), the first-born, Franz (1777–1849), the only son and sole heir, and Charlotte (1782–1843). The Brunsviks lived in a magnificent castle in Martonvásár near Budapest; the family also had a castle in Korompa (Dolna Krupa in Slovakia]).
The children grew up enjoying an education by private teachers, studying languages and classic literature; all four turned out to be talented musicians: Franz became a distinguished violoncellist, the girls excelled at the piano – most of all, Josephine. They admired especially the music of Ludwig van Beethoven, who during the 1790s had established himself as a star pianist in the Austrian capital of Vienna.
In May 1799, Anna took Therese and Josephine to Vienna to ask Beethoven to give her daughters piano lessons. Beethoven later admitted that he had to suppress his love of Josephine, and she felt "enthusiastic" about him. However, it was to the much older Joseph Count Deym (born 1752) to whom she was given in marriage – her mother needed a wealthy son-in-law of equal social standing. After some initial (mainly financial) difficulties, the Deyms developed a reasonably happy relationship, and Beethoven, continuing as Josephine's piano teacher, was a regular visitor. Josephine gave birth to three children in quick succession, and was pregnant with the fourth, when Count Deym died suddenly of pneumonia in January 1804.