.ac is the Internet country code top-level domain (ccTLD) for Ascension Island. 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.

Although it is a ccTLD .ac is offered 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. The University of Kurdistan - Hawler also registers under this top-level domain as http://ukh.ac/, using it as an abbreviation for "academic".