Doctor Samuel Lee Kountz, Jr. (October 30, 1930-December 23, 1981) was an American kidney transplant surgeon from Lexa, Arkansas. He was known for his work in the field of kidney transplants, and in research, discoveries, and inventions in Renal Science. In 1961, He performed the first successful Kidney transplant between humans who were not identical twins. He was also a member of a team of researchers at the University of California, San Francisco, who developed a device that can preserve kidneys for up to 50 hours from the time they are taken from a person's body. It is now used in hospitals and research labs around the world.