Giulietta Simionato (12 May 1910 – 5 May 2010) was an Italian mezzo-soprano. Her career spanned the period from the 1930s until her retirement in 1966. She famously slapped Maria Callas across the face once, although eventually the two became friends.
Born at Forlì, Romagna, she studied in Rovigo and Padua, and made her operatic debut at Montagnana in 1928. In 1928, she sang in Verdi's Rigoletto. The first fifteen years of her career were frustrating, she was only given small parts, but she attracted growing attention in the late 1940s, and by the end of her career was recognised as one of the most respected singers of her generation. In 1936, she made her debut at La Scala and appeared there regularly between 1936 and 1966. She made her debut at the Royal Opera House, Covent Garden in 1953, where she likewise appeared regularly between 1963 and 1965.
Simionato made her United States opera debut in 1953 as Charlotte in Jules Massenet's Werther at the San Francisco Opera with Cesare Valletti in the title role. In 1959 she made her debut at the Metropolitan Opera, as Azucena in Il Trovatore, with Carlo Bergonzi, Antonietta Stella, and Leonard Warren. Simionato also appeared at the Edinburgh Festival (1947), the San Francisco Opera (1953), the Teatro Nacional de São Carlos (1954), the Lyric Opera of Chicago (1954–1961), the Vienna State Opera (from 1956), and the Salzburg Festival. In 1957, she sang in Anna Bolena with Maria Callas. In 1961, she withdrew from three performances at the Metropolitan Opera, with Trigeminal Neuralgia.