In 1970 a paleontological Polish-Mongolian expedition discovered two fragmentary specimens of a small theropod in the Ömnögovĭ province of Mongolia. The type species, "Elmisaurus rarus", was named and described by Halszka Osmólska in 1981. The generic name is derived from Mongol ' or ', "foot sole", as the type specimen consisted of a metatarsus. The specific name means "rare" in Latin. The holotype is ZPAL MgD-I/172, a left metatarsus fused with the tarsalia. There are two paratypes: ZPAL MgD-I/98, consisting of a right hand and foot, and ZPAL MgD-I/20, the upper part of the left metatarsus of a larger individual.