Thomasia is a genus of thirty-one species of flowering plants in the family Malvaceae.

The leaves are simple with leaf-like stipules at the base of the petiole, the flowers bisexual with five papery, petal-like sepals, usually five petals and five stamens opposite the petals.

[2][3][4] The genus Thomasia was first formally described in 1821 by Jaques Étienne Gay in Mémoires du Muséum d'Histoire Naturelle.

[5][6] The name Thomasia honours Pierre Thomas, his son Abraham, and Abraham's sons Philippe, Louis and Emmanuel, a family of Swiss plant collectors.

[6][7] The following is a listed of Thomasia species recognised by the Australian Plant Census as at December 2020:[8]