The .ac top-level domain is the Internet country code (ccTLD) for Saint Helena, Ascension and Tristan da Cunha, used primarily for Ascension Island (Saint Helena has its own ccTLD, .sh). It is administered by NIC.AC, a subsidiary of the Afilias-owned company Internet Computer Bureau.
Registration for the domain is open to anyone. The registry accepts registrations of internationalised domain names.