The Terek Sandpiper (Xenus cinereus) is a small wader and the only member of the genus Xenus.

This bird breeds near water in the taiga of Finland and northern Asia, and migrate south in winter to tropical coasts in east Africa, south Asia and Australia, usually preferring muddy areas. It is a rare vagrant in western Europe. The Terek Sandpiper is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

Slightly larger than the Common Sandpiper at 22-25 cm length, its long upcurved bill makes it very distinctive. As the scientific specific name implies, this wader has a grey back, face and breast in all plumages. The belly is whitish and the legs yellow. The call is a high whistle.

It feeds in a distinctive and very active way, chasing insects and other mobile prey, and sometimes then running to the water's edge to wash its catch. It lays three or four eggs in a lined ground scrape.

Xenus is part of the shank-tattler-phalarope clade and less closely related to the calidrid sandpipers. Based on the degree of DNA sequence divergence and putative shank and phalarope fossils from around the Oligocene/Miocene boundary some 23-22 million years ago, the Terek Sandpiper presumably diverged from their relatives in the Late Oligocene; given the much higher diversity of the prehistoric members of the group in Eurasia it is likely that they originated there, possibly being isolated as the remains of the Turgai Sea dried up, which happened just around this time.