Prostanthera semiteres is a species of flowering plant in the family Lamiaceae and is endemic to Western Australia.

Prostanthera semiteres is a shrub that typically grows to a height of up to 1.4 m (4 ft 7 in) and has hairless branches.

[2][3] Prostanthera semiteres was first formally described in 1984 by Barry Conn in the Journal of the Adelaide Botanic Gardens from specimens collected near Campion by Robert Chinnock in 1976.

[2][4] In the same journal, Conn described two subspecies and the names are accepted by the Australian Plant Census: This mintbush grows between granite rocks in the Avon Wheatbelt, Coolgardie and Mallee biogeographic regions of Western Australia.

[2][3] Both subspecies of P. semiteres are classified as "not threatened" by the Government of Western Australia Department of Parks and Wildlife.