From A Wiki of Ice and Fire
Regicide is the deliberate killing of a monarch. A regicide is condemned.
People accused, suspected or known to have committed regicide
- Khal Drogo - in Vaes Dothrak Khal Drogo gave King Viserys Targaryen the crown of gold he demanded of him, by upending a pot of molten gold over his head, killing him.
- Stannis Baratheon – conceived a shadow assassin with Melisandre that went on to slay his brother King Renly Baratheon.
- Tyrion Lannister – accused of poisoning his nephew King Joffrey Baratheon (of which he is innocent).
- Sansa Stark - along with her husband Tyrion Lannister, Sansa is suspected of poisoning her one time fiancé King Joffrey Baratheon. Cersei is certain Sansa helped Tyrion to murder her son.
- Olenna Redwyne – Littlefinger implies to Sansa Stark that Olenna is the one who poisoned King Joffrey Baratheon at his wedding, with some help from himself and his co-conspirators. Olenna used The Strangler which was disguised as amethysts adorning a hairnet worn by the unwitting Sansa.
- Littlefinger - was a co-conspirator in the successful plot to kill King Jeffrey Baratheon.
- Queen Cersei Lannister - the High Sparrow means to accuse her of killing her husband King Robert Baratheon, (along with high treason, incest, and deicide, all crimes that Osney Kettleblack admitted Cersei had a part to under torture.)
- Euron Greyjoy - suspected by some of organising the death of his brother King Balon Greyjoy, due to his return to the Iron Islands a day after his brothers death.
- Jaime Lannister - during the Sack of King's Landing Jaime breaks his Kingsguard vows and slays King Aerys II Targaryen, by plunging his sword into his back. This earns him the name Kingslayer.
Historical people suspected of regicide
- Viserys II - was suspected of poisoning his own nephew King Baelor the Blessed. Though the evidence on this is dubious and it appears most likely that Viserys was innocent of this charge.
- Lord Stark (grandson of Brandon the Daughterless): Slew Bael the Bard, the King-Beyond-the-Wall. 
|“||“A crown for Cart King!” ||”|
|“||“Joffrey was cruel and stupid, but I did not kill him. Have my head of if you like, I had no hand in my nephew's death.” ||”|
|“||He thrust his longsword through her son’s heart, and twisted.||”|