James Daniel Hardy was a surgeon and researcher practicing in the United States during the twentieth century who studied organ transplantation, or the transfer of an organ from a donor to another individual. In 1963, he performed one of the first recorded lung transplants from a human lung donor. The transplant was successful for three weeks before the patient died of kidney failure. In 1964, Hardy also performed one of the first human heart transplants with a chimpanzee donor, and the transplanted heart pulsed for ninety minutes in the patient’s chest prior to death. He also collaborated on one of the first successful uterus and ovary transplants in a dog, in 1966. Hardy’s research on organ transplantation helped paved the way for improved forms of the technique, which as of 2025 saves the lives of millions of people every year.