This chapter describes the major farmed aquatic animal species from the three main aquaculture groups (finfish, crustaceans, and mollusks). In considering what to include in this chapter, it was recognized that detailed content on the anatomy and physiology of farmed aquatic animals would be several hundred pages long. In contrast, several excellent texts on the biology of finfish, crustaceans, and mollusks and individual species within these groups exist. Thus, to support the disease chapters in this book, it was decided to summarize the following state of knowledge that would allow the reader to recognize each of the major aquaculture animal species or species group: Biology of the species, culture methods, and list of major infectious diseases are reported. It is considered that this information would increase understanding of the information presented in the subsequent chapters about Aquaculture Pathophysiology in this book.