Although freshwaters contribute only about .01% to Earth’s water supply, their fishes now number more than 10,000 species and thus account for at least 40% of all fish species. The continental fish faunas differ greatly in taxonomic composition and species richness, our state of knowledge of them, and the rate of discovery of unknown kinds. The ichthyofaunas of North America (about 1,050 species), Europe (about 360), and Australia-New Guinea (about 500), are the most thoroughly documented, but new species continue to be described based on discovery of previously unseen forms and species-level taxonomic splits of known species. The ichthyofaunas of tropical Asia (perhaps >3,000), Africa (perhaps >3,000 species), and South and Central America (perhaps >>5,000 species), are species rich yet incompletely known. Tropical freshwaters are the hot spots of recent and likely future ichthyological discoveries. Especially in the tropics, discoveries of species that signal new generic-level taxa are common, and new family-level groups are found occasionally. Everywhere on-going phylogenetic studies often suggest or reveal unsuspected relationships. These are times of exciting discovery and advancement of knowledge in freshwater ichthyology. New discoveries beckon us to seek the many remaining unknowns in the diversity of life on our planet. These are also times of rapid and destructive change in freshwater habitats around the globe. These threats alert us to the increasing potential for permanent loss and ignorance of much our planet’s rich aquatic biota.