Pisonia is a genus of flowering plants in the four o'clock flower family, Nyctaginaceae. It was named for Dutch physician and naturalist Willem Piso (1611–1678). Certain species in this genus are known as catchbirdtrees, birdcatcher trees or birdlime trees because they catch birds. The sticky seeds are postulated to be an adaptation of some island species that ensures the dispersal of seeds between islands by attaching them to birds, and also allows the enriching of coralline sands. These island species include P. brunoniana of Australasia and Polynesia and P. umbellifera, which is widespread in the tropical Indo-Pacific region.

Nyctaginaceae, the four o'clock family, is a family of around 33 genera and 290 species of flowering plants, widely distributed in tropical and subtropical regions, with a few representatives in temperate regions. The family has a distinctive fruit type called an accessory fruit or anthocarp, and many genera have extremely large pollen grains.