One of several domain name system (DNS) servers on the Internet that contain the IP addresses of the top level domain (TLD) registry organizations that maintain the global domains (.com, .net, .gov, etc.) and country code domains (.uk, .ca, .fr, etc.). The first point of entry for resolving a domain name, there are currently 34 root servers throughout the world operated by government agencies and private organizations, all of which contain the same data. The original 13 root servers (named A through M), came under a denial of service (DoS) attack in late 2002, and some of them were temporarily knocked out of service. Subsequently, additional servers were deployed.

ISPs and other institutional organizations routinely download copies of the root server tables so that name resolution can be performed locally. There are thousands of these "resolver" computers throughout the Internet that keep the main root servers from becoming overloaded. See DNS and Anycast.