The current study constitutes a revision of herbarium material from the Greater Antilles in different institutions from the insular Caribbean, the United States and Europe; expeditions throughout the area, especially in Cuba and Puerto Rico; as well as the study of both classic and modern literature. As a result, the existing diversity in the Najadaceae, Mayacaceae, Xyridaceae and Haemodoraceae was determined: it consists of five genera and 27 species among which are six species new for the region and four species new for science. Moreover, familial, generic and species descriptions, along with distribution, ecology and conservation state are offered.