Ichthyology (from Greek: ikhthus, "fish"; and logos, "study"), also known as fish science, is the branch of zoology devoted to the study of fish.

This includes bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha).

While a large number of species have been discovered, approximately two hundred and fifty new species are officially described by science each year.

According to FishBase, 33,400 species of fish had been described by October 2016.