Prostanthera calycina, the West Coast Mintbush or Limestone Mintbush, is a spreading perennial shrub that grows to 0.5 m tall. It is endemic to Eyre Peninsula in South Australia. The species has dark green leaves, which smell of mint when crushed. Its red, tube-shaped flowers are about 2 cm long, with petals opening out. A maroon (or sometimes green) outer envelope (calyx) encloses each flower.