Genly Ai: the protagonist of the story and the man who we follow through the majority of the story. He is a man from Ekumen that was sent on a mission to Gethen to try to get them to join their alliance of Ekumen and other planets. He tries for a long time to get them to agree to join their trade alliance but isn't sure how to convince them to do so because he keeps failing. He is very perplexed by the people on this planet and spends a great deal of time observing and learning. Try as he might, he can't really comprehend what is going on in the world around him. He is very confused by the sexuality of the people on Grethen. Coming from a world where there is man and woman he does not understand the androgynous people on Grethen.
Estraven: He starts off the book as the person that helps Ai in his process of getting a meeting with the king. He teaches him things about Karhide and helps him navigate this unknown world. Estraven is the Prime Minister of Karhide but it banished from the country for helping Ai and supposedly conspiring against the king. Once exiled his goes through a few different places before landing in Orgoreyn where he is trying to help Ai and keep him as safe as he possibly can. His main mission is to end the conflict between Ekumen and Gethen to an end peacfully without harming the people of the Sonith Valley.
King Argaven: He is the king of Grethen and doesn't like Estraven and Ai working together because he thinks they want to overthrow him and get the country to change. Argaven does not like change and goes so far as to exile Estraven from his seat as the Prime Minister and banish him from the country to try to get things the way that he wants them. He is terrified of Ai and what his presence means and doesn't wish to hear his proposal out. By the end of the story, the King has gone through some sad stuff like losing the heir to his throne and no longer fears Ai and he no longer fears coming together with the Ekumen, so he signs the treaty.
The Weaver or Faxe: Ai meet Faxe when he comes to Fastness to have his prophecy told to him. Faxe is the guy in charge of Fastness. He gives Ai some peace that Grethen will join the alliance that Ai wishes them to join for his mission to be complete on this planet. He also shows Ai about the type of religion on their planet. Ai had thought that there was no real religion and Faxe teaches him differently. He teaches him about the principles of their religion and that eventually helps Ai survive his journey through the wilderness.
Tibe: one of the antagonists in the novel. He is Estraven's direct opponent and he takes over as the Prime Minister after Estraven is exiled. He uses his platform to spread a very patriotic message across Karhide to gear them up for war against Orgoreyn. Ai has to complete this mission and the mission of bringing Grethen into the fold of their alliance starts with the planet being at peace which starts with communication being restored across the planet. Tibe uses the radio and technology for his own benefit and continues to cause problems for Ai and Estraven in their plan.