[2][3] Prostanthera magnifica was first formally described in 1943 by Charles Austin Gardner in the Journal of the Royal Society of Western Australia from specimens collected near Mullewa by William Blackall.

[4][5] Magnificent prostanthera grows on granite outcrops, ironstone hills and rock crevices in the Avon Wheatbelt, Coolgardie, Geraldton Sandplains, Murchison and Yalgoo biogeographic regions of Western Australia.

[2][3] This mintbush is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.

[2] Prostanthera magnifica prefers a sunny or partly shaded position in well-drained soil.

Grafting is often used to produce a longer-living plant with rootstocks including Westringia fruticosa and Prostanthera striatiflora.