An aerophone () is a musical instrument that produces sound primarily by causing a body of air to vibrate, without the use of strings or membranes (which are respectively chordophones and membranophones), and without the vibration of the instrument itself adding considerably to the sound (or idiophones).

According to Sachs,

Aerophones or 'air instruments' include what are usually called 'wind instruments,' with the addition of a few instruments with a different acoustical principle called 'free aerophones.'
A wind instrument has two essential factors: a tube enclosing a column of air, and a device for setting that air into vibration by interrupting into pulsations the steady breath of the player (or the wind of a bellows).

These may be lips, a mechanical reed, or a sharp edge. Also, an aerophone may be excited by percussive acts, such as the slapping of the keys of a flute or of any other woodwind. A free aerophone lacks the enclosed column of air yet, "cause a series of condensations and rarefications by various means."