Treason is a serious crime against a sovereign or the realm or kingdom as a whole, including rebellion, regicide, oathbreaking, and espionage. A queen consort committing infidelity against the king is also considered treason.
Like oathbreaking, the nature of treason is not an absolute one and is subject to political machinations. It can often depend on whether said treason is successful. While a defeated rebel will be condemned and executed as a traitor, a victorious one will be in power and will merely receive the epithet usurper.
Major cases and accusations of treason
- Ser Duncan the Tall was charged with treason after striking Prince Aerion Targaryen for accosting a woman during a tournament at Ashford. Ser Duncan demanded a trial by combat, which at Aerion's insistence became a trial by seven. Ser Duncan's side was ultimately victorious, but during the combat Aerion's father Prince Maekar Targaryen fatally injured his brother Crown Prince Baelor "Breakspear" Targaryen.
- Brandon Stark, eldest son and heir of Lord Rickard Stark, was arrested for treason by King Aerys II Targaryen after protesting the kidnapping of his sister Lyanna by Prince Rhaegar. When Lord Rickard arrived at the capital to ransom his son, King Aerys arrested him for treason as well. He later has both Starks brutally executed.
- The lords Robert Baratheon, Eddard Stark, Jon Arryn, Hoster Tully and later Tywin Lannister, as well as their bannermen, households, and followers, committed treason against King Aerys when they rebelled against him. However, as they were victorious in their rebellion, they have never been judged as such. Robert Baratheon, however, has become known as "The Usurper" by those who secretly remain loyal to House Targaryen.
- Grand Maester Pycelle betrayed Aerys II when he counseled the Mad King to open the gates of King's Landing to Tywin Lannister when the latter presented himself before the city gates offering protection against the rebellion. Pycelle was aware Tywin did not intend to defend the city.
- Ser Jaime Lannister violated his Kingsguard oath and murdered his king, Aerys II, during the Sack of King's Landing. He was subsequently pardoned by King Robert.
- Eddard Stark, acting in his authority as Hand of the King, decided to move against Prince Joffrey Baratheon and prevent his coronation by taking him prisoner, having discovered that Joffrey has no right to the throne. Petyr Baelish reminded him that such action will be considered treason only if they lose. Baelish and Janos Slynt betray Eddard, who was arrested and executed for treason against Joffrey, accused of seeking to install himself on the Iron Throne.
- The rebellion of the North and the Riverlands to secede from the authority of the Iron Throne is regarded as treason by those who remain loyal to King Joffrey.
- Renly Baratheon committed treason when he tried to take the Iron Throne despite being fourth in the line of succession, ignoring the (false) rights of his nephew Joffrey, Robert's official heir, and the true rights of his older brother Stannis.
- Theon Greyjoy betrayed Robb Stark and joined his father, Balon Greyjoy, in his conquest of the North.
- Rast, a brother of the Night's Watch, killed Lord Commander Jeor Mormont in the Mutiny at Craster's Keep.
- Lord Rickard Karstark, furious over the death of his son Torrhen by Jaime Lannister, accused Catelyn Stark of treason after she released Jaime. Lord Rickard himself was later executed for treason against King in the North Robb Stark for murdering hostages Willem and Martyn Lannister.
- Lords Walder Frey and Roose Bolton committed treason by conspiring with Tywin Lannister to eliminate Robb Stark and his family.
- Alliser Thorne committed treason by organizing the Mutiny at Castle Black that claims Lord Commander Jon Snow's life.
- Lord Smalljon Umber committed treason by handing Rickon Stark over to Ramsay Bolton.
- Petyr Baelish was put on trial by House Stark for conspiring with House Lannister against the Starks, among other accuastions.
- Samwell Tarly told Jon Snow that Daenerys Targaryen shouldn't be queen, and that Jon was the rightful king. Jon spurned the notion as treason.
- Tyrion Lannister was once again accused of treason by Daenerys for freeing his brother against her wishes.
- Talisa Stark: "Your mother is less in need of rescue than any woman I've ever met."
- Robb Stark: "Be kind. She's finally starting to like you."
- Talisa Stark: "And I like her. But if she had her way, I would be back in Volantis playing my harp and you would be sitting over there eating blackberries out of Roslin Frey's hand."
- Robb Stark: "Perhaps I've made a terrible mistake. (Talisa takes a swipe at Robb but he grabs her wrist.) Striking your king is an act of treason."
- — Robb to Talisa Stark[src]
- "You stand accused of murder. You stand accused of treason. How do you answer these charges... Lord Baelish?"
- ―Sansa Stark