A musical instrument of the hand-held bellows-driven free reed aerophone family, invented in Germany and Austria in the 1820s.

Modern accordions consist of a body in two parts, each generally rectangular in shape, separated by a pleated bellows which forces air through tuned metal reeds to produce its sound. On each part of the body is a keyboard containing buttons, levers or piano-style keys. Most, but not all modern accordions also have buttons capable of producing entire chords.

The accordion is distinguished from the concertina by having buttons which travel in a direction perpendicular to the motion of the bellows (towards the player).

Shown is a diatonic 34-button accordion.