Adelaide Tosi (c. 1800 - 27 March 1859) was an Italian operatic soprano.
Born in Milan, Tosi studied with Girolamo Crescentini before making her professional debut in her native city in 1821. She portrayed Azema in the premiere of Giacomo Meyerbeer's L'esule di Granata at La Scala on 12 March 1822. On 7 April 1828, she portrayed Bianca in Vincenzo Bellini's Bianca e Fernando for the grand opening of the Teatro Carlo Felice in Genoa. She returned to that house later that season to sing Pamira in Gioachino Rossini’s Le siège de Corinthe. She went on to portray roles in three world premieres of operas by Gaetano Donizetti at the Teatro di San Carlo in Naples: Argelia in L'esule di Roma (1828), Neala in Il paria (1829), and Elisabetta in Il castello di Kenilworth (1829). On 21 August 1836 she portrayed the title role in the premiere of Donizetti's Betly at the Teatro Nuovo in Naples. She died in Naples at the age of 59.