A contralto is a type of classical female singing voice whose vocal range is the lowest female voice type, with the lowest tessitura. The contralto's vocal range is fairly rare, similar to, but different than an alto, and almost identical to that of a countertenor, typically between the F below middle C (F3 in scientific pitch notation) to the second F above middle C (F5), although at the extremes some voices can reach the E below middle C (E3) or the second B♭ above middle C (B♭5).
"Contralto" is primarily meaningful only in reference to classical and operatic singing, as other traditions lack a system of vocal categorization comparable to that generally accepted in the classical context.  The term "contralto" is only applied to female singers; men singing in a similar range are called "countertenors". The Italian terms "contralto" and "alto" are not synonymous, the latter technically denoting a specific vocal range in choral singing without regard to factors like tessitura, vocal timbre, vocal facility, and vocal weight.
Within the category of contraltos are three generally recognized subcategories—coloratura contralto, lyric contralto, and dramatic contralto—that usefully describe the voice type in general terms. Note, however, that they do not always apply with precision to individual singers; some exceptional dramatic contraltos, such as Ernestine Schumann-Heink and Sigrid Onégin, were technically equipped to perform not only heavy, dramatic music by the likes of Wagner but also florid compositions by Donizetti.
- Coloratura contralto
- Coloratura contraltos—who have light, agile voices ranging very high for the classification and atypically extensive coloratura and high sustaining notes—specialize in florid passages and leaps. Given its deviations from the classification's norms, this voice type is quite rare.
- Lyric contralto
- A lyric contralto voice is lighter than a dramatic contralto but not capable of the ornamentation and leaps of a coloratura contralto. This class of contralto, lighter in timbre than the others, is the most common today and usually ranges from the E below middle C (E3) to the second G above middle C (G5).
- Dramatic contralto
- The dramatic contralto is the deepest, darkest, and heaviest contralto voice, usually having a heavier tone and more power than the others. Singers in this class are rare.
A true contralto is often regarded by some as the most rare of the female voice, and is present in as few as one percent of the population. Some vocal theorists have found that the vocal folds (often incorrectly called "vocal cords") are thicker than those present in other female voices. Studies have used cameras to photograph visible differences which are also found in countertenors.
Contralto roles in opera
True operatic contraltos are rare, and the operatic literature contains few roles written specifically for them. Contraltos sometimes are assigned feminine roles like Angelina in La Cenerentola, Rosina in The Barber of Seville, Isabella in L'italiana in Algeri, and Olga in Eugene Onegin, but more frequently they play female villains or assume trouser roles originally written for castrati. A common saying among contraltos is that they may play only "witches, bitches, or britches."
Examples of contralto roles in the standard operatic repertoire include the following:.
- Angelina*, La Cenerentola (Rossini)
- Art Banker, Facing Goya (Nyman)
- Auntie*, landlady of The Boar, Peter Grimes (Britten)
- Azucena*, Il trovatore (Verdi)
- The Baroness, Vanessa (Barber)
- La Cieca, La Gioconda (Ponchielli)
- Cornelia Giulio Cesare (Handel)
- The Countess*, The Queen of Spades (Tchaikovsky)
- Didone, Egisto (Cavalli)
- Erda, Das Rheingold, Siegfried (Wagner)
- Madame Flora, The Medium (Menotti)
- Fides, Le prophète (Meyerbeer)
- Florence, Albert Herring (Britten)
- Isabella*, L'italiana in Algeri (Rossini)
- Katisha, The Mikado (Gilbert and Sullivan)
- Klytemnestra*, Elektra (Richard Strauss)
- Lel, The Snow Maiden (Rimsky-Korsakov)
- Little Buttercup, H.M.S. Pinafore (Gilbert and Sullivan)
- Lucretia, The Rape of Lucretia (Britten)
- Maddalena*, Rigoletto (Verdi)
- Magdelone, Maskarade (Nielsen)
- Mama Lucia, Cavalleria rusticana (Mascagni)
- Ma Moss, The Tender Land (Copland)
- Malcolm*, La donna del lago (Rossini)
- Margret, Wozzeck (Berg)
- Maria, Porgy and Bess (Gershwin)
- The Marquise of Birkenfeld, La fille du régiment (Donizetti)
- Marthe, Faust (Gounoud)
- Mary, Der fliegende Holländer (Wagner)
- Mother, The Consul (Menotti)
- Mother Goose, The Rake's Progress (Stravinsky)
- Mrs Quickly, Falstaff (Verdi)
- Norn (I), Götterdämmerung (Wagner)
- Olga*, Eugene Onegin (Tchaikovsky)
- Orfeo, Orfeo ed Euridice (Gluck)
- Orsini, Lucrezia Borgia (Donizetti)
- Pauline, The Queen of Spades (Tchaikovsky)
- La Principessa, Suor Angelica (Puccini)
- Ratmir, Ruslan and Lyudmila (Glinka)
- Rosina*, The Barber of Seville (Rossini)
- Rosmira/Eurimene*, Partenope (Handel)
- Ruth, The Pirates of Penzance (Gilbert and Sullivan)
- Smeaton, Anna Bolena (Donizetti)
- Sosostris, The Midsummer Marriage (Tippett)
- Stella, What Next? (Carter)
- Tancredi, Tancredi (Rossini)
- Ulrica, Un ballo in maschera (Verdi)
- Widow Begbick*, Rise and Fall of the City of Mahagonny (Weill)
- 3rd Woodsprite, Rusalka (Dvořák)
* indicates a role that may also be sung by a mezzo-soprano.
Notable operatic contraltos
- Marian Anderson
- Eula Beal
- Clara Butt
- Kathleen Ferrier
- Maureen Forrester
- Marie-Nicole Lemieux
- Ottilie Metzger-Lattermann
- Sigrid Onégin
- Ewa Podleś
- Ernestine Schumann-Heink
- Nathalie Stutzmann
- Hilary Summers
- Category of contraltos
- List of operatic contraltos
- List of contraltos in non-classical music
- Fach, the German system for classifying voices
- Voice classification in non-classical music
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- Chisholm, Hugh, ed. (1911). "Contralto". Encyclopædia Britannica (11th ed.). Cambridge University Press.
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- Media related to Contralto vocalists at Wikimedia Commons
- The dictionary definition of contralto at Wiktionary