The Internet Corporation for Assigned Names and Numbers (ICANN) is an international, nonprofit organization responsible for coordinating Internet Protocol (IP) addresses and domain names. This task includes overseeing companies that register domain names, assigning IP addresses, resolving disputes, maintaining the Whois database of domain name registrars, and maintaining the Domain Name System infrastructure. Although these jobs may seem purely technical in nature, in fact they have serious commercial and legal implications. It thus plays an important role in Internet oversight, regulation, and governance. Its focus has generally been on a bottom-up, open, inclusive, and transparent system of Internet governance, although it is not without its critics. This entry discusses ICANN’s history, organization, activities, and controversies.