Guillaume Rondelet, also known as Rondeletus/Rondeletius, was Regius professor of medicine at the University of Montpellier in southern France and Chancellor of the University between 1556 and his death in 1566. He achieved renown as an anatomist and a naturalist with a particular interest in botany and ichthyology. His major work was a lengthy treatise on marine animals, which took two years to write and became a standard reference work for about a century afterwards, but his lasting impact lay in his education of a roster of star pupils who became leading figures in the world of late-16th century science.

Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of October 2016, with approximately 250 new species described each year.