An occipital bun, also called an occipital spur, occipital knob, chignon hook or inion hook, is a prominent bulge or projection of the occipital bone at the back of the skull. It is important in scientific descriptions of classic Neanderthal crania. It is found among archaic Homo species, as well as Upper Pleistocene Homo sapiens and present-day human populations.

Neanderthals are an extinct group of archaic humans who lived in Eurasia until about 40,000 years ago. The type specimen, Neanderthal 1, was found in 1856 in the Neander Valley in present-day Germany.