The great knot (Calidris tenuirostris) is a small wader. It is the largest of the calidrid species.
The great knot is the largest species of Calidris sandpiper, with its sister species, the red knot, being the next largest. This species has short dark legs and a medium-length thin dark bill. Breeding adults have mottled greyish upper parts with some rufous feathering. The face, throat and breast are heavily spotted black, and there are also some streaks on the rear belly. In winter the plumage becomes uniformly pale grey above. This bird is closely related to the more widespread red knot. In breeding plumage, the latter has a distinctive red face, throat and breast. In other plumages, the great knot can be identified by its larger size, longer bill, deeper chest, and the more streaked upper parts.
These birds forage on mudflats and beaches, probing or picking up food by sight. They mainly eat molluscs and insects.