Thomas Bartholin, Danish physician, mathematician, and theologian (d. 1680)
Thomas Bartholin (; Latinized as Thomas Bartholinus; 20 October 1616 – 4 December 1680) was a Danish physician, mathematician, and theologian. He is best known for his work in the discovery of the lymphatic system in humans and for his advancements of the theory of refrigeration anesthesia, being the first to describe it scientifically.

Thomas Bartholin came from a family that has become famous for its pioneering scientists, twelve of whom became professors at the University of Copenhagen. Three generations of the Bartholin family made significant contributions to anatomical science and medicine in the 17th and 18th centuries: Thomas Bartholin's father, Caspar Bartholin the Elder (1585–1629), his brother Rasmus Bartholin (1625–1698), and his son Caspar Bartholin the Younger (1655–1738). Thomas Bartholin's son Thomas Bartholin the Younger (1659–1690) became a professor of history at the University of Copenhagen and was later appointed royal antiquarian and secretary to the Royal Archives.