Mark Longridge is a Canadian speedcuber known for his Domain of the Cube web page, which was an early cubing website on the World Wide Web in the 1990s.
During the early 1980s Cube craze he attended a Canadian regional Cube contest (London Ontario; February 1982) and an American regional Cube contest (Buffalo, NY; September 1982). In October 1982 Ideal Toys hired him to work as a Rubik's Cube demonstrator.
In February 1990 he released the first issue of his "Domain of the Cube" newsletter. Between 1992 and 1998 he was a regular contributor to the Cube Lovers mailing list. In January 1996 he created his Domain of the Cube web page. The website was an early source of information concerning theory, notation, algorithms, and the history of the Rubik's cube and related puzzles.
The only championship of the modern era he has competed in is World Championship 2003 which took place in Toronto in August 2003.