Julien-Joseph Virey (1775-1846) held the position of pharmacist-in-chief at the Val-de-Grâce, a military hospital. He was an innovative pharmacist, naturalist, anthropologist, and philosopher and a prolific author. His writings encompassed a wide range of topics, although many of his ideas were sometimes harshly questioned. Interest in Virey's work today stems from renewed appreciation of his doctoral thesis in medicine, which was completed in 1814 in Paris and was the first devoted to biological rhythms. Virey envisioned biological rhythms to be innate in origin and controlled by living clocks entrained by periodic environmental changes, such as the day-night alternation in light and darkness. He also reported that the effects of drugs vary according to their administration time. But, above all, he collected and published quantified time series that demonstrated human circadian and annual mortality rhythms. Statistical analysis of Virey's data using modern time series methods confirms his deduction that human mortality exhibits rhythmicity. Comparison of his findings with those derived from analyses of more recent human mortality time series shows the characteristics of these rhythms have changed little since 1807 despite differences in environmental conditions. Virey deserves credit for establishing the field of chronobiology based on his insights and writings.