Trianthema is a genus of flowering plants in the ice plant family, Aizoaceae. Members of the genus are annuals or perennials generally characterized by fleshy, opposite, unequal, smooth-margined leaves, a prostrate growth form, flowers with five perianth segments subtended by a pair of bracts, and a fruit with a winged lid. They are known commonly as horse purslanes. The genus contains about 20 described species growing in tropical and subtropical regions, especially Australia. One common species, Trianthema portulacastrum, Desert Horse Purslane, is frequent as a weed in agricultural areas and is widely distributed.