A species with a large, mouthless head and six eyes on a humanoid body, members of which served in Starfleet in the 2250s and were still seen in the 32nd century.
The Osnullus have one of the most striking designs in Star Trek: Discovery. Their broad heads carry two large eyes and four smaller ones and have no visible mouth, and their skin ranges from pink to purple.
Osnullus officers appear in the background from the first season on, for instance in The Butcher's Knife Cares Not for the Lamb's Cry, and several serve aboard the USS Discovery in 2257 in episodes such as Point of Light and The Red Angel. After the ship's jump to the future, members of the species are seen among the Emerald Chain's enforcers on Hima in That Hope Is You, Part 1 and elsewhere in Scavengers.
The name is never spoken on screen. It comes from the make-up team and loosely means mouthless in Latin.