Karl Patterson Schmidt (June 19, 1890 in Lake Forest, Illinois - September 26, 1957 in Chicago) was an American herpetologist.

Schmidt was the son of George W. Schmidt and Margaret Patterson Schmidt. Schmidt's father was a German professor who, at the time of Schmidt's birth, was teaching in Lake Forest, Illinois. His family left the city in 1907 and settled in Wisconsin. They worked on a farm near Stanley, Wisconsin, where his mother and his younger brother died in a fire on August 7, 1935.[1] The brother, Franklin J. W. Schmidt, was prominent in the then new field of wildlife management.[2]

In 1913 Schmidt entered Cornell University to study biology and geology. In 1915 he discovered his preference for herpetology during a four month training course at the Perdee Oil Company in Louisiana.[3] In 1916 he was admitted to the degree of Bachelor of Arts and made his first geological expedition to Santo Domingo. From 1916 to 1922 he worked as scientific assistant in herpetology at the American Museum of Natural History in New York, under the well-known American herpetologists Mary Cynthia Dickerson and Gladwyn K. Noble. In 1919 he made his first collecting expedition to Puerto Rico. In 1922 he became the assistant curator of reptiles and amphibians at the Field Museum of Natural History in Chicago. From 1923 to 1934 he made several collecting expeditions for that museum to Central and South America, which took him to Honduras (1923), Brazil (1926) and Guatemala (1933-1934). In 1937 he became the editor of the herpetology and ichthyology journal Copeia, which post he occupied until 1949. In 1938 he served in the U.S. Army. In 1941 he became the chief curator of zoology at the Field Museum, where he remained until his retirement in 1955. From 1942 to 1946 he was the president of the American Society of Ichthyologists and Herpetologists (ASIH). In 1953 he made his last expedition, which was to Israel.

In 1957 he died from the consequences of the bite of a juvenile boomslang, which had been sent to his lab at the Field Museum in Chicago for identification by Marlin Perkins (who was then the director of the Lincoln Park Zoo). He underestimated the severity of this strike, which occurred 28 hours before his death and he failed to submit himself to medical treatment.

Schmidt was one of the most important herpetologists in the 20th century. Though he made only a few important discoveries by himself, he named more than 200 species. There are many species named "karlschmidti" in his honour. He wrote more than 200 articles and books, including Living Reptiles of the World which became an international bestseller.