United HealthCare is the largest provider of medical health coverage in the United States and reaches more than 130 countries globally. With over 300,000 employees, it is also one of the world's largest corporations.
In the United States in particular, United Healthcare is competitive in the group employer coverage space and also offers some good individual and family plans including Medicare and Medicaid offerings. In addition, they have a very large contracted network of physicians and other medical providers.