Thereianthus is a small genus of cormous plants from the Southwestern Cape of South Africa in the Iridaceae family. They are unusual for a winter rainfall climate as most species bloom in the dry warm summer months. Flowers are blue, purple, or white.

Thereianthus minutus is a South African endemic species from the WesCape Province where it is usually found in Fynbos growing on rock ledges, damp cliffs, streamsides and peaty seeps from Groot Winterhoek to Kogelberg and the western Riviersonderend Mountains. It was previously known as Thereianthus lapeyrousioides, Watsonia lapeyrousioides and Watsonia minuta. It grows to 10cm tall with dainty purple flowers in spring. This is a very showy plant when planted in a tiny pot or planted en masse. It likes to be crowded together.