G visa:

Employees of international organizations, such as the United Nations, the World Health Organization, the World Bank, the IADB, etc. may be accorded G visas. This is a quasi-diplomatic visa category, also not based on a petition because it does not count as U.S. employment.

Like diplomats in A visa status, G employees and their dependent family members are required to be registered with the State Department during their stay. Some G dependents are eligible for employment authorization, depending on reciprocal agreements with the home country.