Mayo Clinic is a nonprofit medical practice and medical research group based in Rochester, Minnesota. It is the first and largest integrated nonprofit medical group practice in the world, employing more than 3,800 physicians and scientists and 50,900 allied health staff. The practice specializes in treating difficult cases through tertiary care. It spends over $500 million a year on research.

Dr. William Worrall Mayo settled his family in Rochester in 1864 and opened a medical practice that evolved under his sons into Mayo Clinic. Mayo Clinic is widely regarded as one of the world's greatest hospitals and ranked No. 1 on the 2014–2015 U.S. News & World Report List of "Best Hospitals", maintaining a position near the top for more than 20 years. It has been on the list of America's "100 Best Companies to Work For" published by Fortune magazine for eight consecutive years. It continued to achieve this ranking through 2015.

In addition to their flagship hospital in Rochester, the Mayo Clinic has major campuses in Arizona and Florida. The Mayo Clinic Health System also operates affiliated facilities throughout Minnesota, Wisconsin, and Iowa.