A suborder of trilobites (a class of extinct arthropods) and a diverse clade consisting of roughly 100 distinct species; they are among the first trilobites and thus the first definitive metazoans to appear in the fossil record. Olenellina first appear in rocks from Scandinavia and eastern Europe that are roughly 530 million years old; they persisted until the end of the Early Cambrian, roughly 510 million years ago. Their extinction coincided with a widespread global extinction.

They are known from all of the Earth's major Cambrian continents with fossiliferous strata, except Australia, Antarctica, and the south China region of Asia, but they reached their greatest abundance and diversity in North America. Charles Walcott, the famous paleontologist associated with the discovery of the Burgess Shale, did some of the first important studies on them.