What is the smallest bone in the human body?

The smallest bone in the human body is the stirrup bone, also called the stapes.

The stapes sits in the middle ear and is the third of three auditory ossicles: the malleus, incus, and stapes—better known as the hammer, anvil, and stirrup. Its footplate rests against the oval window, transmitting vibrations into the fluid-filled inner ear so they can be converted into nerve signals for hearing.

The name “stapes” comes from the Latin word for “stirrup,” because the bone’s shape resembles the metal support used by a rider’s foot. It is only a few millimetres long, making it both the smallest and lightest bone in the human skeleton. Anatomists commonly credit Giovanni Filippo Ingrassia with its discovery in 1546, although the history of that attribution is debated.

A common mix-up is confusing the smallest bone with the coccyx, or tailbone. The coccyx is small compared with major limb bones, but it is made of several fused vertebrae. Another nearby fact is that the stapedius, a tiny muscle attached to the stapes, is often described as the smallest skeletal muscle in the human body.