Solitary to colonial, terrestrial, mostly glabrous herbs with fleshy ovoid tubers. Leaf basal, sheathing at base, linear to lanceolate, rarely ovate-lanceolate or terete. Flowering stem long, smooth; stem-bracts (1–)2(–4). Inflorescence racemose, mostly loose, bracteate, 1–20-flowered. Flowers with column uppermost; ovary obovoid or ovoid, not clearly delineated from pedicel or perianth; all perianth segments similar in size and colour (labellum may differ slightly in shape), glabrous, usually opening fully only on hot and humid sunny days, colour variable (sometimes within species), usually scented. Column erect, short, broadly winged, joined in front below the stigma, produced laterally about the level of the anther into 2 lateral lobes (column-arms) which are terete or flat, variously tuberculate, fimbriate and/or terminated by a hair-tuft; accessory lobes sometimes arising behind the column-arms (sometimes considered to be a lateral expansion of mid-lobe); mid-lobe (extension of the column between the column-arms; sometimes called post-anther lobe) may be crested, bifid or trifid, or sometimes forms a hood or flap over the anther; anther visible or concealed, erect or inclined, the connective often extending into a long tip; stigma borne in front of or below the anther, with viscid disc, upper lobe of stigma reniform.
Over 110 species and several described hybrids mostly restricted to temperate Australia: 20 species in New Zealand (14 endemic) and a few species in Indonesia, New Caledonia, New Guinea and the Philippines. 43 species and 5 named hybrids in Victoria.
Thelymitra latifolia R.J.Bates has been reported from Victorian sites (e.g. Casterton area, Rheola), but no supporting specimens have yet been detected in Australian herbaria. Its formal acceptance as a member of the Victorian flora awaits confirmation. This otherwise South Australian species closely resembles T. peniculata and other members of the T. pauciflora complex, but is distinguished by a relatively broad, flat leaf with its sinus at or almost at ground level. The perianth segments are pale to mid blue or mauve, 6–10 mm long and open briefly and only in warm humid weather. The column resembles that of T. peniculata, but the post-anther lobe is not dilated and not or barely cleft.