Kingslaying

"Is that what you tell yourself at night? That you're a servant of justice? That you were avenging my father when you shoved your sword in Aerys Targaryen's back?"

- Ned Stark to Jaime Lannister

Kingslaying, also known as regicide is the deliberate act of murdering a monarch and is considered the most severe crime in the Seven Kingdoms. Whoever commits it is dubbed a kingslayer.

Like kinslaying, incest, or violating guest right, kingslaying is considered an abomination to the Faith of the Seven.

Known and alleged kingslayers
"The Lannisters send their regards."

- Roose Bolton to Robb Stark




 * Ser Jaime Lannister, perhaps the most notable example of a kingslayer, who murders Aerys II Targaryen during the Sack of King's Landing. Jaime's actions were considered especially shameful, as he was in fact a member of Aerys' Kingsguard, and took a holy vow to lay down his life in defence of his king


 * Khal Drogo murdered Viserys Targaryen by pouring molten gold onto his head. Despite technically being the rightful king of Westeros, Viserys himself was an exile at the time, and never actually sat upon the Iron Throne.


 * Queen Cersei Lannister, along with her cousin Lancel, conspired to bring about the death of her husband King Robert Baratheon. On Cersei's instruction Lancel replaced the wine in the king's flask with a stronger, fortified vintage, causing Robert to quickly descend into an intoxicated state, dulling his reflexes, and ultimately leading him to suffer a fatal wound upon a boar's tusk.
 * King Stannis Baratheon, who conceives a shadow assassin with Melisandre to kill his brother Renly. This may not be considered a true example of kingslaying, as Renly himself was a usurper, and was in open rebellion against his elder brother, the rightful king.


 * Lord Roose Bolton betrayed and murdered his own King, Robb Stark, during the massacre known as the "Red Wedding".

In the books
In the A Song of Ice and Fire novels, the taboo against kinslaying is much the same.