The Amazon and Orinoco basins in northern South America are home to the highest concentration of freshwater fish species on earth, with more than 3,000 species allotted to 564 genera. Amazonian fishes include piranhas, electric eels, freshwater stingrays, a myriad of beautiful small-bodied tetras and catfishes, and the largest scaled freshwater fish in the world, the pirarucu. Field Guide to the Fishes of the Amazon, Orinoco, and Guianas provides descriptions and identification keys for all the known genera of fishes that inhabit Greater Amazonia, a vast and still mostly remote region of tropical rainforests, seasonally flooded savannas, and meandering lowland rivers.