Species delimitation is the process of determining which groups of individual organisms constitute different populations of a single species and which constitute different species. The problem goes back to the earliest days of taxonomy and formalized processes for describing new species exist and are widely used, although the methods are time-intensive and problematic for some species. Genomic data carries extensive information about the degree of genetic isolation among species and about ancient and recent introgression. For this reason, genomic data can play an important role in species delimitation under many existing species concepts. Here we review the history of molecular species delimitation leading up to the current genomic era. We then describe the most widely used computational methods for species delimitation using single-and multi-locus genomic data. Relative strengths and weaknesses of the approaches are discussed and a new method for delimiting species based on empirical criteria is proposed.