The stapes or stirrup is the stirrup-shaped small bone or ossicle in the middle ear which attaches the incus to the fenestra ovalis, the "oval window" which is adjacent to the vestibule of the inner ear. It is the smallest and lightest bone in the human body.

The stapes transmits the sound vibrations from the incus to the membrane of the inner ear inside the fenestra ovalis.

In non-mammalian vertebrates, the bone homologous to the stapes is usually called the columella; however, in reptiles, either term may be used.