Many poisons are used throughout the Seven Kingdoms and in the East. The Maesters of the Citadel study the histories and qualities of various poisons in addition to their healing arts, but their use seems to be more widespread in the Free Cities and the assassins' guilds. Poisons are also used in the further east, such as in Meereen, and in Qarth, where the Pureborn are notorious for offering poisoned wine to those they consider dangerous. 
- See also: Images of Poison
Poison is regarded with fear and loathing by knights and high lords alike in the feudal society of the Seven Kingdoms. The poisoner is considered to be beneath contempt, and that no true man kills with poison. Poison is felt to be a weapon of cravens and cowards, eunuchs, women, and Dornishmen.
Common poisons include nightshade, derived from a plant, and powdered greycap, derived from a variety of toadstool. Animal and insect venoms such as basilisk and manticore venom are also known to be used, though they are harder to gather. Manticore venom is particularly vicious and can be treated to make it work more slowly, causing its victim to die in slow agony. Every hedge maester knows the common poisons.
Rare poisons include the strangler, which is made from a plant found only in the Jade Sea. It kills by closing the windpipe and therefore suffocating its victims. It is a poison that has been used in the past to kill kings, a reason many kings now employ food-tasters.
There are also ambiguous poisons. Moon tea aborts pregnancies, which makes some maesters reluctant to call it a medicine. Sweetsleep brings deep sleep in small doses, but larger doses can kill. Large enough doses of most medicines can be fatal; the difference with sweetsleep is that the fatal dose is still quite small relative to other medicines. A maester must therefore be very careful when administering it. Some poisons do not kill, but only make the victim indisposed for a time.
Poisons are commonly administered to victims in food or drink, which can also serve to mask their taste and odor. Because of this, noble kitchens are often guarded, and food tasters are employed to protect their masters' lives with their own. Even so, clever poisoners manage to slip past the safeguards from time to time, and at least as many nobles' deaths are caused by a poisoned cup or dish as by a bloodied blade, if not more so. Poison may also be delivered by coating a weapon or even through the skin. An assassin may even coat a gold coin with poison, and pass it to the target who is poisoned when he bites the coin to test its value.
List of known poisons
Characters known to use poison
Characters known to have been poisoned
- Alequo Adarys
- King Aegon II Targaryen
- Maester Cressen
- Lord Edgar Yronwood
- Eladon Goldenhair
- Gaemon Palehair
- Ser Gregor Clegane
- Harren Botley
- Ser Hobert Hightower
- King Joffrey Baratheon
- Lord Jon Arryn
- Loyal Spear
- Magister Ordello
- Strong Belwas - survived
- Ulf the Sot
- The Waif - survived
- House Blackwood's weirwood
- Queen Alys Harroway's child, poisoned in her womb
Characters suspected to have been poisoned
Survivors of attempted poisonings
The poisoner is beneath contempt.
—thoughts of Cressen
Poison is a foul and filthy way to kill.
—Lysa Tully, to Petyr Baelish
I begged Lord Arryn to use a taster, in this very room I begged him, but he would not hear of it. Only one who was less than a man would even think of such a thing, he told me.
I was weaned on venom, Dalt. Any viper takes a bite of me will rue it.
Poisoners invariably choose the choicest dishes.—the Tattered Prince
We know more of [poison] in the Free Cities. It is the tears, never doubt it. The old maester would have seen it soon enough, so he had to die first. That is how I would do it. Not that I would. Poison is ... dishonorable.
- A Game of Thrones, Chapter 25, Eddard V.
- A Clash of Kings, Chapter 40, Daenerys III.
- A Dance with Dragons, Chapter 56, The Iron Suitor.
- A Game of Thrones, Chapter 33, Eddard VIII.
- A Clash of Kings, Prologue.
- A Feast for Crows, Chapter 34, Cat Of The Canals.
- A Feast for Crows, Chapter 23, Alayne I.
- A Feast for Crows, Chapter 41, Alayne II.
- A Clash of Kings, Chapter 25, Tyrion VI.
- A Feast for Crows, Prologue.
- A Dance with Dragons, Chapter 64, The Ugly Little Girl.
- The Sons of the Dragon.
- A Dance with Dragons, Chapter 38, The Watcher.
- A Storm of Swords, Chapter 80, Sansa VII.
- A Game of Thrones, Chapter 30, Eddard VII.
- A Dance with Dragons, Chapter 60, The Spurned Suitor.
- Fire & Blood, Birth, Death, and Betrayal Under King Jaehaerys I.