Bioluminescence is defined as the emission of light from a living organism that performs some biological function. Bioluminescence is one of the oldest fields of scientific study, dating from the first written records of the ancient Greeks.  This article describes the many investigations of animal luminescence up to the end of the 19^th Century. Many facets of this field are easily accessible for investigation without need for advanced technology and so, within the History of Science, investigations of bioluminescence played a significant role in the establishment of the scientific method, and also were among the many visual phenomena to be accounted for in developing a theory of light.