The rock sandpiper (Calidris ptilocnemis) is a small shorebird in the sandpiper family Scolopacidae. This is a hardy sandpiper that breeds in the arctic and subarctic regions of Alaska and the Chukotka and Kamchatka Peninsulas. It is closely related to the purple sandpiper that breeds in arctic regions of northeast Canada and the northwest Palearctic.
Adults have short yellow legs and a medium thin dark bill. The body is dark on top with a slight purplish gloss and mainly white underneath. The breast is smeared with grey and the rump is black. The Pribilof Islands subspecies of this bird shows a bold black belly patch.