Cypripedium calceolus is a lady's-slipper orchid, and the type species of the genus Cypripedium.
It has a widespread distribution from Europe east through Asia to the Pacific Ocean and is typically is found in open woodland on moist calcareous soils. In continental Europe it is also found growing in the decomposed humus of semi-shaded woodland cover on limestone. It has declined over much of the European part of its range, and as a result is legally protected in a number of countries.
In Britain it was formerly a reasonably widespread plant across northern England, particularly the limestone area of the Yorkshire Dales. By the late 20th century it had declined to just a single plant in one location in the dales. While the virtual extinction of the Lady's-slipper orchid from its historical range in Britain is often blamed on uprooting by gardeners and botanists, it is also the case that its preferred habitat shrunk markedly with human clearance of woodland from the limestone landscape, and the grazing of sheep will have finished it off. A reintroduction program for the Lady’s-slipper orchid is in place, and has led to a population of hundreds of plants as of 2003.
The Norwegian municipality of Snåsa has a Cypripedium calceolus in its coat-of-arms.
In Pavel Ivanovich Melnikov's "In the Forests", a znakharka (Russian wise woman) calls this Adam's head, Adam's grass, and Cuckoo's slippers and says it is good for every ill including driving away evil spirits.
Cypripedium calceolus sensu stricto ("in the strict sense") does not occur in North America. The closely related Cypripedium parviflorum and C. pubescens are often still referred to as subspecies or variety of C. calceolus.