A bass is a type of male singing voice and possesses the lowest vocal range of all voice types. According to The New Grove Dictionary of Opera, a bass is typically classified as having a range extending from around the second E below middle C to the E above middle C (i.e., E2–E4). Its tessitura, or comfortable range, is normally defined by the outermost lines of the bass clef.

The low extreme for basses is generally C2 (two Cs below middle C). However, several extreme bass singers are able to reach much lower than this.

Within opera, the lowest note in the standard bass repertoire is D2 (Osmin), but few roles fall below F2. Although Osmin's note is the lowest 'demanded' in the operatic repertoire, lower notes are heard, both written and unwritten: for example, it is traditional for basses to interpolate a low C in the duet "Ich gehe doch rathe ich dir" in the same opera. Other optional or traditional low Cs and Ds are sung. The high extreme: a few bass roles in the standard repertoire call for a high F♯ or G (F♯4 and G4, the one above middle C), but few roles go over F4. In the operatic bass repertoire, the highest note is a G♯4 (The Barber in The Nose by Shostakovich); the aria "Fra l'ombre e gl'orori" in Handel's cantata Aci, Galatea e Polifemo calls for an A4.