An organization responsible for assigning domain names for the TLD that they manage. Furthermore, it is their responsibility to update the global DNS tables that all nameservers use to resolve domain names.

Before July, 1999, the U.S. Top Level Domain Registry for (.com .net and .org) was the responsibility of a single company by contract with the U.S. Department of Commerce. Beginning in July 1999, a Shared Registry System has been in place.