Marianna Marchesa Florenzi, née Marianna Bacinetti, was born in Ravenna, Italy, to a wealthy, aristocratic family. Her parents were Count Pietro Bacinetti and his wife Countess Laura Rossi. Marianna received an usually broad education for a girl of her era. At age seven, she began attending the Colegio Santa Chiara in Faenza, where she read widely in philosophy. When she was 15, her parents arranged her marriage to the marchese Ettore Florenzi of Perugia, three times her age, making her a marchesa. She became one of the first women in the 19th century to study natural sciences at the University of Perugia. In 1821, at the age of 18, she met Crown Prince Ludwig of Bavaria, later King Ludwig I, during Carnivale in Rome. They began an intense relationship that lasted 40 years until his death. Some historians state that they were lovers, others believe it was a platonic, intellectual relationship. She visited Ludwig more than 30 times and wrote him some 2,000 letters. He constantly sought her advice, including on government matters. After the death of her first husband, Marianna married Evelyn Waddington, an Englishman living in Perugia, and devoted herself to the study of philosophy, writing and translating.
Under the name Marianna Florenzi Waddington, she translated Gottfried Leibniz's book Monadology into Italian and also translated and promoted the works of Kant, Hegel, Spinoza and Schelling.
She became a witty hostess and presided over a popular salon.
She was the only woman admitted to the Reale Accademia di Scienze morali et politiche di Napoli. In 1842, she traveled to Paris, where she met the French philosopher Victor Cousin and played an important role in introducing the German philosophers to France.
Her published works included Riflessioni sul Socialismo e Comunismo (Thoughts on Socialism and Communism, 1850).
Filosofemi di Cosmologia e di Ontologia (1863), Saggi di Psicologia e di Logica (1864), Saggio su la Natura (1866), Saggio sulla Filosofia dello Spirito (1867), and Della Immortalita dell' Anima Umana (1868). Several of these works wound up on the Roman Catholic Church's index of banned books.