Cosima Wagner (born Francesca Gaetana Cosima Liszt; 24 December 1837 – 1 April 1930) was the illegitimate daughter of the Hungarian pianist and composer Franz Liszt and Marie d'Agoult. She became the second wife of the German composer Richard Wagner, and with him founded the Bayreuth Festival as a showcase for his stage works; after his death she devoted the rest of her life to the promotion of his music and philosophy. Commentators have recognised Cosima as the principal inspiration for Wagner's later works, particularly Parsifal.
In 1857, after a childhood largely spent under the care of her grandmother and with governesses, Cosima married the conductor Hans von Bülow. 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; after his death in 1883 she directed the Bayreuth Festival for more than 20 years, increasing its repertoire to form the Bayreuth canon of ten operas and establishing the festival as a major event in the world of musical theatre.
During her directorship, Cosima opposed theatrical innovations and adhered closely to Wagner's original productions of his works, an approach continued by her successors long after her retirement in 1907. She 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 which closely followed her death in 1930. Thus, although she is widely perceived as the saviour of the festival, her legacy remains controversial.
In January 1833 the 21-year-old Hungarian pianist and composer Franz Liszt met Marie d'Agoult, a Parisian socialite six years his senior. Marie's antecedents were mixed; her German mother, from a prominent Frankfurt banking family, had married a French nobleman, the Comte de Flavigny. Marie had been married since 1827 to Charles, Comte d'Agoult, and had borne him two daughters, but the union had become sterile. Drawn together by their mutual intellectual interests, Marie and Liszt embarked on a passionate relationship. In March 1835 the couple fled Paris for Switzerland; ignoring the scandal they left in their wake, they settled in Geneva where, on 18 December, Marie gave birth to a daughter, Blandine-Rachel.