Isocarpha oppositifolia, the Rio Grande pearlhead, is a New World species of plants in the sunflower family. It is widely distributed in eastern and southern Mexico, Central America, the West Indies (Cuba, Jamaica, Bahamas, Caymans, Trinidad), and northern South America (Colombia, Venezuela). The range extends northward, just barely crossing to the north side of the Río Grande in the two southernmost counties in Texas (Cameron + Hidalgo).