Lynn Thorndike (born 1882 in Lynn, Massachusetts, USA; died 1965) was an American historian of medieval science and alchemy. Among his books on magic and science are: A History of Magic and Experimental Science (8 vol., 1923–58), spanning the period from early Christianity through early modern Europe; and Science and Thought in the Fifteenth Century (1929). Thorndike also wrote The History of Medieval Europe (1917, 3d ed. 1949) and translated the medieval astronomical textbook De sphaera mundi of Johannes de Sacrobosco.

Thorndike began teaching medieval history at Northwestern University in 1907. He moved to Western Reserve University in 1909 and stayed there until 1924. Columbia University lured him away in Fall 1924 and he taught there until he retired from teaching in 1950. Thorndike continued to publish for an additional ten years and in 1957 received the Sarton Medal from the History of Science Society.

He believed in contradicting the famous Swiss historian Jacob Burckhardt. Instead of viewing the Italian Renaissance