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 and the alto are the two most commonly used saxophones. The tenor is pitched in the key of B♭ (while the alto is pitched in the key of E♭), 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", "tenor sax players", or "saxophonists".

The tenor saxophone uses a larger mouthpiece, reed and ligature than the alto and soprano saxophones. Visually, it is easily distinguished by the curve in its neck, or its crook, near the mouthpiece. The alto saxophone lacks this and its neck goes straight to the mouthpiece. The tenor saxophone is most recognized for its ability to blend well with the soprano, alto and baritone saxophones, with its "husky" yet "bright" tone.

Tenor sax has been an important solo instrument in jazz music. Famous and influential players include Coleman Hawkins, Lester Young, Ben Webster, Dexter Gordon, Wardell Gray, Stan Getz, Sonny Rollins, John Coltrane and Wayne Shorter. The work of younger players such as Michael Brecker and Chris Potter has been an important influence in more recent jazz.