Gnidia is a genus of flowering plants in the family Thymelaeaceae. It is distributed in tropical and southern Africa and Madagascar; more than half of all the species are endemic to South Africa. Gnidia was named for Knidos, an Ancient Greek city located in modern-day Turkey.

These are perennial herbs and shrubs, sometimes with rhizomes. Most species have alternately arranged leaves, and a few have opposite leaves. The leaves are undivided and unlobed. The inflorescence is a head of a few to many flowers. The calyx is cylindrical and the colored lobes may alternate with the petals; some species lack petals. Many species are similar in appearance and difficult to tell apart.

Molecular analyses have provided evidence that the genus is polyphyletic, made up of four different lineages. They are related to the four genera Struthiola, Drapetes, Lasiosiphon, and Pimelea.

Formerly 140 to 160 species were classified in the genus. Many have been reassigned to other genera and Plants of the World Online currently accepts 104 species.

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