Cartonema is a genus of perennial or annual monocotyledonous flowering plants in the dayflower family. It is restricted to Australia and nearby Trangan Island, which is part of Indonesia. It is the earliest diverging member of its family and has a number of traits that are unique within it, such as non-succulent leaves and a lack of raphides (a particular form of calcium oxalate). Its distinctive features led to the genus to once be considered part of its own separate family, Cartonemataceae. However, analysis of DNA sequences, as well as many common anatomical characters, has supported its relationship with the Commelinaceae. It contains about 11 species.