The long-tailed ground squirrel or Eversmann's souslik (Urocitellus undulatus) is a species of rodent in the squirrel family Sciuridae. It is found in China, Kazakhstan, Mongolia, and Russia.

The long-tailed ground squirrel has a compact, low-slung body, short legs and a long bushy tail. The body length reaches up to 315 millimetres (12.4 in) and the tail 160 millimetres (6.3 in). The back is brown with a linear pattern of dark, small spots. The underparts are a paler ochre-brown with a reddish tinge along the side. The tail is barred in brown and black with a prominent light edge stripe and a pale tip.

This species is found in submontane steppes up to 3,100 metres (10,200 ft), plains, meadows, the edges of pine forests and birch woods, clearings and agricultural land from Southern Siberia and Altai (Russia) to Manchuria. There are two isolated populations in Eastern Siberia, one in southeastern Yakutia and the other in the south of the Amur region. It also occurs in Mongolia and in the northwestern and northeastern parts of China.