Treason
Treason was the act of betraying one's country, organization, affiliation, or ally, usually to assist the enemy. The most severe cases were sometimes called high treason. One who committed this act was known as a traitor.

Use of the term
Treason was one of the very few crimes punishable by death on  in the 22nd century. ()

In 2257, following the disappearance of the  into a wormhole, Spock suggested that all information on the ship, its crew and the spore drive be sealed and any attempt to mention them would be brought up as treason. This was to prevent the discovery of the ship's true mission and prevent the return of Control. ()

In 2259 of the alternate reality,  asked Captain  to beam him off the , noting that he had committed treason against Admiral  by sabotaging the ship. ()

Various Starfleet-related acts of treason and traitors have been uncovered throughout history.

In 2365, Worf told Geordi La Forge, who was being held captive by Pakleds, that it would be treasonous to give them classified tactical information. This was part of a ruse to rescue La Forge by making the Pakleds believe he was a weapons expert. ()

In 2368, Toral, son of Duras stood convicted of treason for his role in the Klingon Civil War and attempt to take the role of Chancellor from Gowron. His life was given to Worf to do with what he wished. Worf chose to spare him. ()

In 2370, Data told William T. Riker that he could not give orders because of the charges he faced upon his return from Arctus Baran's ship, having been declared a renegade. Treason was one of the charges he mentioned. ()

Tom Paris was convicted of treason for his activities with the Maquis and sentenced to eighteen months' imprisonment at the New Zealand Penal Settlement. ()

, Lauren and Patrick almost committed treason in 2374, by trying to give Weyoun and Damar Starfleet battle plans and fleet deployments. ()

The Female Changeling was determined that Damar "pay a price" for his treason against the Dominion. She ordered Weyoun to find Damar's wife and children. () 

General Martok considered it treasonous to challenge Chancellor Gowron's leadership of the Klingon Empire in the middle of the Dominion War. ()

In 2390 in an alternate timeline, in which the  crashed in the Takara sector, Harry Kim and Chakotay were wanted on two counts of high treason and conspiracy to violate the Temporal Prime Directive for their plan to prevent the incident from happening. ()

Known acts of treason
 Khitomer conspiracy
 Khitomer Massacre
 Klingon Civil War
 Mutiny

External link
 

fr:Trahison
Crimes