.ac is the Internet country code top-level domain (ccTLD) for Saint Helena, Ascension and Tristan da Cunha. It is administered by NIC.AC, a subsidiary of the Internet Computer Bureau based in the United Kingdom.
Registration for this domain is open to anyone. The registry accepts registrations of internationalized domain names.
.ac is marketed by some domain-brokers as a domain for the city of Aachen in Germany, using the analogy to the automotive license plate designation (“AC”) for the city.