Gary McKinnon (born 10 February 1966) is a Scottish systems administrator and hacker who has been accused of what one U.S. prosecutor claims is the "biggest military computer hack of all time," although McKinnon himself states that he was merely looking for evidence of free energy suppression and a cover-up of UFO activity and other technologies potentially useful to the public.

US authorities claim that McKinnon is trying to downplay his own actions. A senior military officer at the Pentagon told The Sunday Telegraph: "US policy is to fight these attacks as strongly as possible. As a result of Mr McKinnon's actions, we suffered serious damage. This was not some harmless incident. He did very serious and deliberate damage to military and Nasa computers and left silly and anti-America messages. All the evidence was that someone was staging a very serious attack on US computer systems."

After a series of legal proceedings in England, McKinnon is currently fighting extradition to the United States.