Habenaria elongata, commonly known as the white rein orchid, or Kimberley spider orchid, is a species of orchid that is endemic to northern Australia. It has up to four leaves at its base and up to twenty small white flowers with yellowish tips and thread-like lobes on the labellum.
Habenaria elongata is a tuberous, perennial herb with between two and four oblong to egg-shaped leaves at its base, the leaves long and wide. Between eight and twenty white flowers with yellow tips, long and wide are borne on a flowering stem tall. The sepal is long, about wide, overlapping with the base of the petals to form a hood over the column. The sepals are long, about wide and turn downwards behind the labellum. The petals are about long and wide. The labellum turns downwards and has three lobes, the side lobes very narrow linear to thread-like, long and the middle lobe long. The nectary spur is curved and long. Flowering occurs in January and February.
Habenaria elongata was first formally described in 1810 by Robert Brown and the description was published in Prodromus Florae Novae Hollandiae et Insulae Van Diemen. The specific epithet (elongata) is a Latin word meaning "prolonged", referring to the three long labellum lobes.
The white rein orchid is found in the Kimberley region of Western Australia, northern parts of the Northern Territory, on the Cape York Peninsula and in New Guinea. It grows in grassland, open forest and woodland.