Fibiger, Johannes Andreas Grib (1867-1928) was a Danish pathologist and bacteriologist who did early work on diphtheria and tuberculosis and proved that medical research could play a decisive role in public health. In 1926, Fibiger won the Nobel Prize in physiology or medicine for the first controlled induction of cancer in laboratory animals.

Fibiger was 3 years old when his father, a physician, died. He then moved with his mother and sister to Copenhagen, where he grew up. He began his studies in medicine, biology, and zoology at the University of Copenhagen in 1883 at age 16. He received his medical degree from the university in 1890. He became interested in pathological research while serving as laboratory assistant to bacteriologist C. J. Salomonsen, who encouraged him to do doctoral research on the diphtheria bacterium. By demonstrating that there were two distinct forms of the bacillus, Fibiger contributed to the identification of asymptomatic carriers of the disease, which was a serious public health problem at the time. His serum against diphtheria earned him international renown.

He successfully defended his doctoral dissertation-based on his diptheria research–at the University of Copenhagen in 1895. Five years later, he became director of the Institute of Pathological Anatomy at the University of Copenhagen. There, Fibiger conducted research on tuberculosis in cattle and humans. By demonstrating that drinking the milk of infected cattle could cause humans to develop tuberculosis, Fibiger's research led to the passage of laws governing the sale of raw milk and thus to fewer deaths from tuberculosis.

Fibiger became interested in cancer research in 1907, when he found stomach tumors in three tubercular rats. He discovered that the tumors were caused by cockroaches infected by round-worm larvae. By 1913, Fibiger was able consistently to induce gastric tumors in mice and rats by feeding them such cockroaches and thus, became the first researcher to control induction of cancer in laboratory animals.