Ai is the main character of the story, often called "Genry" by the Karhiders, who have trouble pronouncing the letter "L" in their language. At the start of the book, he has been on Gethen for one year attempting to join Gethen with the Ekumen as the first mobile and an envoy of the Ekumen. He arrived with basic information about the language and culture from a team of investigators who had come before him. In Karhide, the king is reluctant to accept his diplomatic mission. In Orgoreyn, Ai is seemingly accepted more easily by the political leaders, yet Ai is arrested, stripped of his clothes, drugged, and sent to a work camp. Rescued by Estraven, the deposed Prime Minister of Karhide, Genly realizes that cultural differences – specifically shifgrethor and gender roles and Gethenian sexuality – had kept him from understanding their relationship previously. During their 81 day journey across the frozen land to return to Karhide, Ai learned to understand and love Estraven.
Therem Harth rem ir Estraven is a Gethenian from the Domain of Estre in Kerm Land. He is the King's Ear (first minister) until exiled from Karhide after attempting to assuage the Sinnoth Valley Dispute with the Orgota. Estraven attempts to help Genly in his Ekumenical pursuits by guiding him, although under the rules of shifgrethor direct advice is an insult, and aiding him with his political influence. Estraven made a societally-incorrect kemmering vow to his brother, Arek Harth rem ir Estraven, after they had produced a child together and therefore his vow made with Ashe is a "false vow, a second vow".
King Argaven Harge XV is the current king of Karhide. He is described as being "mad" and his behavior is certainly paranoid. He gave audience to Genly Ai, but refused the Ekumen alliance and exiled Estraven for treason. He has sired seven children but has yet to bear "an heir of the body, king son".
Commensal Obsle of the Sekeve District is an Orgota who once headed the Orgota Naval Trade Commission in Erhenrang. He is a short, inquisitive Orgota Commensal with small eyes, who seeks power and prestige for himself and for his government and wants to invite the Ekumen to Orgoreyn.
Pemmer Harge rem ir Tibe is King Argaven's cousin. Tibe is prone to orating and becomes the King's Ear after the exile of Estraven and becomes Regent after King Argaven becomes pregnant. Tibe is fervently against Genly Ai's mission and seems to want to start a war with Orgoreyn. He has Estraven killed at the Karhide/Orgoreyn border.