.su is an Internet country code top-level domain (ccTLD) that was designated for the Union of Soviet Socialist Republics (USSR) on 19 September 1990.

[4][5][6] After 1989 a set of new internet domains was created in Europe, including .pl (Poland), .cs (Czechoslovakia), .yu (Yugoslavia) and .dd (East Germany).

[8] On 26 December 1991 the country was dissolved and its constituent republics gained independence, which should have caused the domain to begin a phase-out process, as happened with those of East Germany, Czechoslovakia, and Yugoslavia.

[7] In 2001, the managers of the domain stated that they would commence accepting new .su registrations, but it is unclear whether this action was compatible with ICANN policies.

[14] The domain has been reported to host many cybercrime activities[15][5][4] due to the relaxed and outdated terms of use, along with staying out of focus (2% usage comparing to the primary .ru zone).