The alto flute is an instrument in the Western concert flute family, pitched below the standard C flute and the uncommon flûte d'amour. It is the third most common member of its family after the standard C flute and the piccolo. It is characterized by its rich, mellow tone in the lower portion of its range. The bore of the alto flute is considerably larger in diameter and longer than the C flute and requires a larger column of air (volume of air) from the player, though it also requires a slower airspeed. This gives it a greater dynamic presence in the bottom octave and a half of its range. Its range is from G3 (the G below middle C) to G6 (4 ledger lines above the treble clef staff) plus an altissimo register stretching to D♭7. It uses the same fingerings as the C flute and piccolo, but is a transposing instrument in G (sounding a perfect fourth lower than written).

The western concert flute family has a wide range of instruments.