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, is arrested for treason by King Aerys II Targaryen after protesting the kidnapping of his sister Lyanna by Prince Rhaegar. When Lord Rickard arrives at the capital to ransom his son, King Aerys arrests 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, commit treason against King Aerys when they rebel against him. However, as they are victorious in their rebellion they are never judged as such. Robert Baratheon, however, becomes 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, decides to move against Prince Joffrey Baratheon and prevent his coronation by taking him prisoner, having discovered that Joffrey is a bastard born of incest with no right to the throne. Petyr Baelish reminds him that such action will be considered treason only if they lose. Baelish and Janos Slynt then betray Lord Stark, who is arrested and then 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 betrays Robb Stark and joins his father, Balon Greyjoy, in his conquest of the North.
- Rast, a brother of the Night's Watch, kills 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, accuses Catelyn Stark of treason after she releases Jaime in exchange for her daughters, Sansa Stark and Arya Stark. Lord Rickard himself is later executed for treason against King in the North Robb Stark for murdering hostages Willem and Martyn Lannister.
- Lords Walder Frey and Roose Bolton commit treason when they conspire with Tywin Lannister to eliminate Robb Stark and his family.
- Tyrion Lannister is put on trial for the regicide of King Joffrey.
- In the Telltale game depending on who Ethan Forrester didn't select to be his Sentinel, Ser Royland Degore, the master-at-arms of Ironrath or Duncan Tuttle, the Castellan of Ironrath, betrays House Forrester by relaying information to their rivals House Whitehill. Can be executed by Rodrik Forrester for their treason.
- Cersei Lannister is arrested by the Faith Militant for the regicide of her husband King Robert after one of their members, her cousin and former lover Lancel, informed against her to the High Sparrow.
- Alliser Thorne commits treason by organizing the Mutiny at Castle Black that claims Lord Commander Jon Snow's life. However, Thorne and his fellow Mutineers are later defeated by those still loyal to Snow with help from the wildlings, and Snow is later resurrected by Melisandre. Snow then executes Thorne along with Othell Yarwyck, Bowen Marsh, and Olly by hanging.
- Lord Smalljon Umber commits treason by handing Rickon Stark over to Ramsay Bolton.
- Petyr Baelish is put on trial by House Stark for murdering his wife Lysa Arryn, whom he had previously given Tears of Lys to poison her previous husband Jon Arryn; conspiring with House Lannister to betray Eddard Stark, which led to his imprisonment and execution on false charges of treason; and essentially igniting the War of the Five Kings all so he could acquire more and more power. When all his crimes are laid bare, Baelish is summarily executed by Arya Stark.
- Samwell Tarly tells Jon Snow that Daenerys shouldn't be queen, and that Jon is the rightful king. Jon spurns the notion as treason.
- Tyrion Lannister is once again accused of treason by Daenerys for freeing his brother against her wishes, and is subsequently arrested by the unsullied.
- 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