The soprano saxophone is a variety of the saxophone, a woodwind instrument, invented in 1840. The soprano is the third smallest member of the saxophone family, which consists (from smallest to largest) of the soprillo, sopranino, soprano, alto, tenor, baritone, bass, contrabass and sub-contrabass.

A transposing instrument pitched in the key of B♭, modern soprano saxophones with a high F# key have a range from A♭3 to E6 and are therefore pitched one octave above the tenor saxophone. Some saxophones have additional keys, allowing them to play an additional F♯ and G at the top of the range. These extra keys are commonly found on more modern saxophones. Additionally, skilled players can make use of the Altissimo register, which allows them to play even higher. There is also a soprano pitched in C, which is less common and has not been made since around 1940.

The soprano saxophone can be compared to the B♭ clarinet. Although the clarinet can play a diminshed fifth lower and over a fifth higher, the sax generally has a louder and more penetrating sound in the extreme high notes. Due to the smaller bore of the soprano, it is less forgiving with respect to intonation, though an experienced player will use alternate fingerings or vary breath support, tongue position, or embouchure to compensate. Professional players will use the technique of voicing to fix problems with intonation. Due to its similarity in tone to the oboe, the soprano saxophone is sometimes used as a substitute for it.