It has a single leathery, dark green leaf and up to twenty blue to purplish or pink flowers with fringed lobes and yellowish hair tufts on top of the column.

[2][3][4] Thelymitra circumsepta was first formally described in 1878 by Robert Fitzgerald from a specimen he collected on Mount Tomah.

[6]: 121 The naked sun orchid grows in swampy, high rainfall districts from near the coast to subalpine areas.

[7] Only between ten and twenty individuals of this species are known from South Australia and it is listed as "endangered" in that state.

The main threats to the species there are competition with coral fern and altered water regimes.