Cosima was the illegitimate daughter of the composer-pianist Franz Liszt and the countess Marie d’Agoult, with whom Liszt also had two other children.
Liszt not only legitimatised the births of his children, but also provided generously for their education and dowries.
Cosima was educated in Paris by the governess of her father’s mistress, Princess Wittgenstein, and then at the house of the mother of Hans von Bülow in Berlin. In 1857 she married Hans von Bülow, one of the outstanding conductors of his time and a favourite pupil of Liszt.
Although the marriage produced two children, it was largely a loveless union, and in 1863 Cosima began a relationship with Wagner, who was 24 years her senior. She married him in 1870. In that year, too, Wagner composed the Siegfried Idylle to commemorate the birth of their son, Siegfried (1869–1930).
With the passing of Wagner in 1883, Cosima took upon herself the management of the Bayreuth Festivals, of which she was art director until 1907, when her son Siegfried took over.
She applied her characteristic energies and her continued devotion to Wagner’s works. She was the moving force behind the festival plays in both commercial and social matters, influencing the selection of repertory, artists, and style of presentation.
Cosima shared Wagner's convictions of German cultural and racial superiority, and under her influence, Bayreuth became increasingly identified with antisemitism. This was a defining feature of Bayreuth for decades, into the Nazi era.
Cosima died in Bayreuth in total blindness in 1930.
