The freshwater copepods are a group with very interesting ecological characteristics; their real importance in the continental aquatic ecosystems is unquestionable; however, there is scarce knowledge of them. These microcrustaceans are found mainly in tropical zones; in Mexico, a large quantity of continental bodies of water exist whose copepod fauna remains completely unknown. In the case of the Yucatan Peninsula, efforts have not been sufficient to characterize the copepod fauna. Without a doubt, a factor associated with the scarce regional knowledge of this group is the difficulty in its taxonomic study, which requires the management and dissection of specimens of 0.3 mm to 2 mm in length.

The objective of this paper is to contribute to the knowledge of the copepods found in the bodies of water of the Yucatan Peninsula. This work required the meticulous revision of extensive taxonomic literature of the group and other specialized literature. It was complemented with the analysis of our own field and laboratory data, including collections originating from more than 30 dispersed localities in several zones of the peninsula. The specimens are described in simple female and male forms and represent more than 30 species in those zones. A key is devised for the identification of the copepods found in the samples analyzed.