The Terek sandpiper (Xenus cinereus) is a small migratory Palearctic wader species and is the only member of the genus Xenus. It is named after the Terek River which flows into the west of the Caspian Sea, as it was first observed around this area. The genus name Xenus is from Ancient Greek xenos stranger, and cinereus is Latin for "ash-grey" from cinis, cineris, "ashes".