American microbiologist who was corecipient, with Hamilton Othanel Smith (Smith, Hamilton Othanel) of the United States and Werner Arber (Arber, Werner) of Switzerland, of the 1978 Nobel Prize for Physiology or Medicine. The three scientists were cited for their discovery and application of restriction enzymes (restriction enzyme) that break the giant molecules of deoxyribonucleic acid (DNA) into fragments, making possible the study of the genetic information they contain. The process constitutes one of the basic tools of genetic research.

The son of Russian immigrants, Nathans attended the University of Delaware and Washington University in St. Louis, Missouri, where he earned a medical degree in 1954. He became a professor of microbiology at Johns Hopkins University in Baltimore, Maryland, in 1962 and director of its department of microbiology in 1972; he also briefly served as the school's interim president (1995–96).

In his prizewinning research, Nathans used the restriction enzyme isolated by Smith from the bacterium Haemophilus influenzae to investigate the structure of the DNA of the simian virus 40 (SV40), the simplest virus known to produce cancerous tumours. This achievement, the construction of a genetic map of a virus, heralded the first application of restriction enzymes to the problem of identifying the molecular basis of cancer. His work also played an important role in the development of prenatal tests for such genetic diseases as cystic fibrosis and sickle cell anemia. In 1993 Nathans was awarded the National Medal of Science.