Aristolochia (English /əˌrɪstəˈloʊkiə/) is a large plant genus with over 500 species that is the type genus of the family (Aristolochiaceae). Its members are commonly known as birthwort, pipevine or Dutchman's pipe and are widespread and occur in the most diverse climates. Some species, like A. utriformis and A. westlandii, are threatened with extinction. Isotrema is usually included here, but might be a valid genus. If so, it contains those species with a three-lobed calyx.