What is the ISO code for Antarctica?

ISO 3166-1 alpha-2 (2 digits) for Antarctica:

The ISO 3166-1 code for Antarctica is: AQ

Each country, or geographical entity, or province, or department, etc. has been awarded codes defined in ISO 3166 by the International Organization for Standardization (ISO).
ISO 3166-1 alpha-2: two-letter codes are used for many applications, including top-level domains for each country.