Karl Oskar Medin (14 August 1847 – 24 December 1927) was a Swedish pediatrician. He was born at Axberg, Örebro and died in Stockholm. He is most famous for his study of poliomyelitis, a condition sometimes known as the Heine-Medin disease, named after Medin and another physician, Jakob Heine. Medin was the first to describe the epidemic character of infantile paralysis. In addition to his research of poliomyelitis, he had influenced the study of meningitis epidemica, infant scurvy and tuberculosis in children.