Mario Ramberg Capecchi is an Italian-born molecular geneticist and a co-awardee of the 2007 Nobel Prize in Physiology or Medicine for discovering a method to create mice in which a specific gene is turned off, known as knockout mice. He shared the prize with Martin Evans and Oliver Smithies. He is currently Distinguished Professor of Human Genetics and Biology at the University of Utah School of Medicine.

The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, according to Alfred Nobel's 1895 will, are awarded "to those who, during the preceding year, have conferred the greatest benefit to humankind". Nobel Prizes are awarded in the fields of Physics, Medicine or Physiology, Chemistry, Literature, Economics and Peace.