Prostanthera behriana, commonly known as tall mintbush,[2] is a species of flowering plant in the family Lamiaceae and is endemic to the south-east of South Australia.

It is an erect to straggling shrub with egg-shaped leaves and white, pale blue, pale violet or purplish white flowers with red-brown spots or purple streaks inside.

The flowers are arranged singly in leaf two to fourteen leaf axils near the ends of branchlets, each flower on a pedicel 0.5–1 mm (0.020–0.039 in) long.

The petals are 15–20 mm (0.59–0.79 in), white, pale blue, pale violet or purplish white with red-brown spots or purple streaks inside, and fused to form a tube 7–10 mm (0.28–0.39 in) long.

[3][4] Prostanthera behriana was first formally described in 1847 by Schlechtendal in the journal Linnaea from specimens collected by Hans Hermann Behr.