Lynn Thorndike (born 24 July 1882, in Lynn, Massachusetts, USA; died 28 December 1965, at Columbia University Club, New York City) was an American historian of medieval science and alchemy. Thorndike studied at Wesleyan University, Middletown, Connecticut (Bachelor of Arts, 1902), and then medieval history at Columbia University (Master of Arts 1903, Doctorate 1905). Thorndike's doctoral dissertation (1905) was about "The Place of Magic in the Intellectual History fo Europe", which he went on to link with the historical development of experimental science. He 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 also served as president of the American Historical Association. Counter to Swiss historian Jacob Burckhardt who argued that the Italian Renaissance was a separate phase, Thorndike believed that most of the political, social, moral and religious phenomena which are commonly defined as Renaissance seemed to be almost equally characteristic of Italy at any time from the twelfth to the eighteenth centuries. 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 to the end of the 17th century; 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.

His works include-
The Place of magic in the intellectual history of Europe 1905
The True Roger Bacon 1916
History of medieval Europe, 1917
Medieval Europe, its development & civilization, 1920
Galen: the man and his times 1922
Peter of Abano: a medieval scientist 1923
History of magic and experimental science. 1923
Dates in intellectual history: the fourteenth century. 1945
Check-list of rotographs in the history of natural and occult science 1934
Traditional medieval tracts concerning engraved astrological images. 1947
Sphere of Sacrobosco and its commentators. 1949
Outline of medieval and modern history 1929
Science and thought in the fifteenth century; studies in the history of medicine and surgery, natural and mathematical science, philosophy, and politics. 1963
Michael Scot. 1965
University records and life in the Middle Ages 1975