A eunuch is a man who has been castrated or emasculated, before or after puberty. Most people would not volunteer their young sons to become eunuchs, and most men would not choose to be castrated or emasculated. Therefore, most eunuchs are slaves who have had no choice in the matter. The most famous eunuchs are the Unsullied.
Eunuchs in Essos
Eunuchs are far more common in Essos than Westeros, where they make popular slaves. In Yunkai, slaves are made into eunuchs by cutting only the testicles off.  The Yunkai'i also geld boys in order to produce castrati slaves. Yurkhaz zo Yunzak owns a group of Yunkish castrati slaves who sing songs in the ancient tongues of the Old Empire. Their voices are high and sweet and impossibly pure. The Dothraki dosh khaleen are served by eunuchs. In the Seven Kingdoms poison is seen as a weapon of eunuchs.
In Bayasabhad, Kayakayanaya and Shamyriana 99 of 100 boys, the sons of the Great Fathers, are gelded when they reach the age of manhood and live out their lives as eunuchs, serving their cities as scribes, priests, scholars, servants, cooks, farmers, and craftsmen. Only the most promising males, the largest, strongest, and most comely, are permitted to mature, breed, and become Great Fathers in their turn.
The priests of the Blind God, a deity that was once worshiped in the Valyrian Freehold, were eunuchs who wore eyeless hoods in honor of the god, for only in darkness, they believed, would their third eye open.
Eunuchs in Westeros
In Westeros castration appears to serve more as a severe punishment and deterrent. Varys is a known eunuch who has risen to the influential and powerful position of Master of Whisperers. However, he was made a eunuch in Myr, not Westeros.
- The priests of the Blind God
- The Nine Eunuchs - (voluntarily emasculated)
- Lord Varys - (emasculated)
- The Unsullied of Astapor (emasculated)
- Strong Belwas
- Almost all of the sons of the Great Fathers
- Ser Lucamore Strong – (castrated) - gelded as punishment.
- Ser Tyland Lannister – (castrated) - gelded when under torture.
- Rodrik Greyjoy - taken to Casterly Rock as a captive where Lady Johanna Lannister had him gelded and made him her son's fool.
- Eunuch strangler
- Septon Bernard - gelded as punishment.
- Meizo Mahr
- Ser Jon Cafferen
- The "Surly lad" who impregnated Coryanne Wylde.
- The rapists of King's Landing Prince Daemon Targaryen gelded when he was Commander of the City Watch.
- Eight rapers were gelded during the Feast Day of Our Father Above in 133 AC.
- Lord Bartimos Celtigar - (castrated) - gelded by Wat the Tanner when under torture during the Dance of the Dragons.
- Lord Gargon Qoherys - gelded by Harren the Red when under torture and bled to death.
- Soldiers in Stannis Baratheon's army gelded (castrated) on his orders for raping three wildings women. These soldiers are later left behind at the Wall as part of Melisandre's guards when the king rides south.
A eunuch has no honor, and a spider does not enjoy the luxury of scruples, my lord.
I've never been quite sure what the point of a eunuch is, if truth be told. It seems to me they're only men with the useful bits cut off.—the Queen of Thorns
Even those who lack a man’s parts may still have a man’s heart, Your Grace.
“Have you ever heard such singing , my love?” Hizdahr asked her. “They have the voices of gods, do they not?” “Yes,” she said, “though I wonder if they might not have preferred to have the fruits of men.”
What does a eunuch know of a man's honor?
- The fact that Theon has his penis removed by Ramsay in "The Bear and the Maiden Fair", an episode of Game of Thrones written by George R. R. Martin, may be a confirmation of Greyjoys's emasculation in the books. However, in the DVD commentary of the episode, even though Martin explained that in the books the Greyjoy lost bits of his body left to the imagination of the readers, he clarified that actually did not write any of the scenes with Theon and Ramsay for Game of Thrones: (Spoilers Extended) Unused elements in GRRM's GOT scripts revealed in commentary tracks, (reddit.com).
- A Storm of Swords, Chapter 23, Daenerys II.
- A Dance with Dragons, Chapter 60, The Spurned Suitor.
- A Game of Thrones, Chapter 46, Daenerys V.
- A Game of Thrones, Chapter 25, Eddard V.
- A Dance with Dragons, Chapter 36, Daenerys VI.
- The World of Ice & Fire, The Grasslands.
- A Feast for Crows, Chapter 13, The Soiled Knight.
- The World of Ice & Fire, The Free Cities: Lorath.
- The World of Ice & Fire, The Bones and Beyond: Yi Ti.
- A Clash of Kings, Chapter 44, Tyrion X.
- A Storm of Swords, Chapter 63, Davos VI.
- The World of Ice & Fire, The Bones and Beyond.
- Fire & Blood, The Long Reign - Jaehaerys and Alysanne: Policy, Progency, and Pain.
- The World of Ice & Fire, The Westerlands: House Lannister Under the Dragons.
- The World of Ice & Fire, The Red Kraken.
- Fire & Blood, The Lysene Spring and the End of Regency.
- A Clash of Kings, Chapter 29, Tyrion VII.
- A Storm of Swords, Chapter 10, Davos II.
- Fire & Blood, Reign of the Dragon - The Wars of King Aegon I.
- Fire & Blood, A Surfeit of Rulers.
- Fire & Blood, Heirs of the Dragon - A Question of Succession.
- Fire & Blood, Under the Regents - War and Peace and Cattle Shows.
- Fire & Blood, The Dying of the Dragons - Rhaenyra Overthrown.
- The World of Ice & Fire, The Targaryen Kings: Aenys I.
- A Dance with Dragons, Chapter 31, Melisandre I.
- A Storm of Swords, Chapter 75, Samwell IV.
- A Dance with Dragons, Chapter 20, Reek II.
- A Dance with Dragons, Chapter 37, The Prince of Winterfell.
- A Game of Thrones, Chapter 58, Eddard XV.
- A Storm of Swords, Chapter 6, Sansa I.
- A Dance with Dragons, Chapter 11, Daenerys II.
- A Dance with Dragons, Chapter 24, The Lost Lord.