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

The petals are mauve to light purple but paler on the inside of the tube, with mauve to reddish-brown dots, 10–15 mm (0.39–0.59 in) long and form a tube 8.5–10 mm (0.33–0.39 in) long.

[2][3] Prostanthera splendens was first formally described in 1988 by Barry Conn in the journal Nuytsia from specimens collected by Charles Gardner near Mount Barloweerie in 1931.

[2][4] This mintbush grows in pebbly soil on breakaways in the Coolgardie and Mallee biogeographic regions of Western Australia.

[2][3] Prostanthera splendens is classified as "Priority One" by the Government of Western Australia Department of Parks and Wildlife,[3] meaning that it is known from only one or a few locations which are potentially at risk.