Small to large terrestrial, lithophytic, or rarely epiphytic herbs. Roots elongate, fibrous; rhizome short to elongate. Stems unbranched, obscure to long, erect, leafy. Leaves distichous, 1 to many, plicate or conduplicate, spreading or suberect, green, rarely checkered or tessellated with dark and lighter green or spotted with blackish maroon adaxially, thinly textured, fleshy, or leathery, glabrous or variously pubescent, entire. Inflorescence terminal, 1- to several flowered; rachis hairy, glandular, or glabrous; bracts conduplicate. Flowers usually showy; pedicel obscure to short; ovary 1-locular or 3-locular, glabrous or hairy, lacking an abscission layer. Dorsal sepal erect or hooded over lip, ovate, obovate, or elliptic, obtuse, acute, or acuminate, glabrous or pubescent on outer surface, sometimes pubescent within at base; lateral sepals usually fused to form a concave synsepal ± similar to dorsal sepal, rarely free to base (in Cypripedium plectrochilum). Petals free, spreading or pendulous, spiraling or not, elliptic, ovate, linear, or oblanceolate, glabrous or rarely pubescent on outer surface, usually ciliate on margins, sometimes warty on margins; lip deeply pouched, slipper-shaped or urn-shaped, with or more rarely without ± pronounced incurved side lobes sometimes reduced to auricles, hairy within especially on lower surface, sometimes spotted within, glabrous or hairy on outer surface; front margin incurved or not, sometimes with short marginal horns; side lobes sometimes warty. Column short, stalked, porrect; anthers 2, 2-locular, borne on short obtuse to acute filaments; pollen powdery or viscid; staminode terminal, sessile or shortly stalked, often shield-shaped, transversely reniform, oblong, ovate, obcordate, or linear, flat, convex or longitudinally conduplicate, glabrous to papillose or finely pubescent; stigma stalked or subsessile, dependent, convex, 3-partite, ± papillose. Capsule erect to pendulous, 3-ribbed, cylindric to almost ellipsoidal, sometimes beaked at apex. Seeds ellipsoidal with a thin testa.
Five genera and ca. 180 species: widespread in the temperate regions of Eurasia and North America, the tropical Americas south to Brazil and Bolivia, and tropical SE Asia to the Philippines, New Guinea, and the Solomon Islands; two genera and 63 species (27 endemic) in China.
China is a center of diversity for the genera Cypripedium and Paphiopedilum.