High Treason

High treason is criminal disloyalty to one's government. Participating in a war against one's native country, attempting to overthrow its government, spying on its military, its diplomats, or its secret services for a hostile and foreign power, or attempting to kill its head of state are perhaps the best known examples of high treason. High treason requires that the alleged traitor have obligations of loyalty in the state he or she betrayed, such as citizenship, although presence in the state at the time is sufficient. Foreign spies, assassins, and saboteurs, though not suffering the dishonor associated with conviction for high treason, may still be tried and punished judicially for acts of espionage, assassination, or sabotage, though in contemporary times, foreign spies and saboteurs are usually repatriated following capture. High treason is considered a very serious crime.

Historically, in common law countries, high treason was differentiated from petty treason, which was the act of killing a lawful superior (such as a servant killing his or her master or mistress). It was, in effect, considered a more serious degree of murder. As jurisdictions around the world abolished petty treason, the concept of petty treason gradually faded, and today use of the word "treason" generally refers to "high treason."

Until the 19th century, counterfeiting coins was high treason in the United Kingdom and its predecessor countries.