Vittoria Tesi ("La Fiorentina") (Florence, 13 Feb 1700 – 9 May 1775 in Vienna) was an Italian opera singer and music teacher of the 18th century. Her vocal range was that of a contralto.
Her operatic career began with performances at Parma and Bologna in 1716. By 1718 she was virtuosa di camera for the Prince of Parma at Venice. The following year she was at Dresden, singing for Antonio Lotti alongside Senesino and Margherita Durastanti. By 1721 she was back in Italy for the Florentine Carnival, and for the next 26 years travelled Europe, with performances in Madrid and possibly Frankfurt. Italy, however, was the nation where she spent most of her time, dividing the years between its various cities. Her career peaked in the late 1730s and 1740s, when she sang alongside such singers as Caffarelli; in 1744 she took the title role in Gluck's Ipermestra and did the same in 1748 in his Semiramide riconosciuta, set to a libretto by Metastasio. This performance persuaded Metastasio of her merits, although previously he had been unenthusiastic, calling her a "grandissima nullità".
After successful performances in Niccolò Jommelli's Achille in Sciro and Didone abbandonata (1749), both set to Metastasian libretti, Tesi began to retire from the stage. In 1751 she became costume director at the Viennese court, where she remained for many years, teaching music as a particular favourite of Countess Maria Theresia Ahlefeldt. Among her pupils were Caterina Gabrielli and Elisabeth Teyber, and she is known to have met not only Casanova but also Mozart and his father. Sarah and Ange Goudar called her "perhaps the first actress who acted well while singing badly", and in fact both Charles Burney and Quantz praised her acting ability.