Chaenostoma is a genus of flowering plants belonging to the family Scrophulariaceae. Its native range is Southern Tropical and Southern Africa. The genus name, Chaenostoma, means gaping mouth.

Chaenostoma caeruleum, synonymously known as Buchnera viscosa, Diascia karasmontana, Erinus viscosus, Manulea caerulea, Manulea rotata, Manulea viscosa, Sphenandra coerulea, Sphenandra viscosa or Sutera caerulea is a South African endemic species from the Eastern Cape and Western Cape Provinces. Chaenostoma caeruleum is an erect, perennial shrublet reaching 1m in height. Being single-stemmed it does not resprout after fire in the wild. The leaves are up to 3 cm long, 1 cm wide and typically have sparsely toothed margins that are rolled under. Leaves and young stems are covered in gland-tipped hairs. The mauve-pink flowers grow in long racemes. They are star-shaped with rounded petal lobes spreading to a diameter of around 1,5cm. Flowering occurs in winter and spring.