The inion (plural: inia/inions) is the tip of the external occipital protuberance (EOP), the midline bony prominence in the occipital bone from which the ligamentum nuchae and trapezius muscle attach. It is usually easily palpable.

It is the surface marking of the internal attachment of the tentorium cerebelli.

It is one of the skull landmarks, craniometric points for radiological or anthropological skull measurement.