The tenor saxophone is a medium-sized member of the saxophone family, a group of instruments invented by Adolphe Sax in the 1840s. The tenor, with the alto, are the two most common types of saxophones. The tenor is pitched in the key of B♭, and written as a transposing instrument in the treble clef, sounding an octave and a major second lower than the written pitch. Modern tenor saxophones which have a high F# key have a range from A♭2 to E5 (concert) and are therefore pitched one octave below the soprano saxophone. People who play the tenor saxophone are known as "tenor saxophonists", or more commonly "tenor sax players".

The tenor saxophone uses a slightly larger mouthpiece, reed, and ligature than the alto and soprano saxophones. It is easily distinguished from these instruments by the bend in its neck, or its crook, near the mouthpiece.

The tenor saxophone is used in many different types of ensembles, including concert bands, big band jazz ensembles, small jazz ensembles, and marching bands. It is occasionally included in pieces written for symphony orchestra and for chamber ensembles; three examples of this are Ravel's Boléro, Prokofiev's suite from Lieutenant Kijé,and Webern's Quartet for violin, clarinet, tenor saxophone, and piano. In concert bands, the tenor plays mostly a supporting role, sometimes sharing parts with the euphonium, horn and trombone. In jazz ensembles, the tenor plays a more prominent role, often sharing parts or harmonies with the alto saxophone.