Ludvig Hektoen (July 2, 1863 – July 5, 1951) was an American pathologist known for his work in the fields of pathology, microbiology and immunology. Hektoen was appointed to the National Academy of Sciences in 1918, and served as president of many professional societies, including the American Association of Immunologists in 1927 and the American Society for Microbiology in 1929. He was the founding editor of the Archives of Pathology and Laboratory Medicine in 1926 and edited several other medical journals. He was knighted to the Order of St. Olav in 1929, and in 1933, he became professor emeritus of pathology at the University of Chicago. The Hektoen Institute for Medical Research—formerly the John McCormick Institute of Infectious Diseases—now bears his name.