Coleoptera: Elmidae and Protelmidae contains a complete list of subfamilies, tribes, subtribes, genera, subgenera, species and subspecies, and their synonyms described before 2015. Protelmidae are here elevated from tribal rank to family rank. Other new nomenclatorial and taxonomic acts include a new substitute name, seven new generic and specific synonymies, four new combinations, two designations of type species and eight mandatory corrections of incorrect original spellings. Detailed information about the geographical distribution of each species is provided. This catalogue includes extant taxa (147 genera and 1497 species of Elmidae, four genera and six species of Protelmidae) and fossil taxa (two genera and five species of Elmidae). It is the first world catalogue of Elmidae published since 1910. Unavailable names are listed as well. Detailed explanations are provided concerning the availability and correct spelling of taxa names, correct identity and spelling of author names, correct publication dates, and correct type localities.