Dietes grandiflora, commonly named fortnight lily, large wild iris, African iris[1] or fairy iris, is a rhizomatous perennial plant of the family Iridaceae with long, rigid, sword-like green leaves.

This species is common in horticulture in its native South Africa, where it is often used in public gardens, beautification of commercial premises and along roadsides.

Dark markings are found at the base of the outer tepals.

Plants prefer dappled shade to full sun where they will flower in profusion, though they will grow in shaded areas (with an accompanying loss of flower production).

Dietes grandiflora are drought and frost hardy, making them popular for en masse plantings.