Major Characters

Ender
Ender is a small boy, only six years old when the novel begins, and not much older than ten years old when he defeats the buggers. He is a Third, but permitted by the government to be born because he has the superior intelligence of the Wiggin children and a disposition that is kinder than Peter's, but not as sensitive as Valentine. As such, Ender is able to do well in Battle School and go on to successfully command the human mission to the bugger home world in Command School, but he regrets the deaths he has caused, and is glad for the chance the hive queen presents of trying to redeem himself.

Valentine
The sister of Ender, she consistently comes to his defense, whether it be when Peter threatens him, or when she feels that Graff is suggesting that Ender is mentally similar to Peter. Although she agrees to go along with Peter's plan for keeping the world united by taking on the identity of Demosthenes in her writings on the nets, she believes that her ability to persuade by flattery along with her other strengths (such as equal mental abilities) will, in the end, make her stronger than Peter. She is able to use that power to keep Ender from going back to Earth, where she is sure that he would fall under Peter's control, and instead takes him to the colony, where she writes a history of the war.

Peter
The oldest of the Wiggin children, Peter uses threats and violence in order to control those around him. Despite having tortured a squirrel in the woods, he admits that he fears becoming evil, and takes on the identity of Locke in order to influence events. When the bugger war ends, he ends the fighting on Earth through the Locke Proposal, and becomes Hegemon, basically ruling the world.

Graff
Although the character appears only at the beginning of the chapters and then sporadically through the events, he is the main adult character in the novel. It is Graff who decides what will be done to Ender in order to shape him into a commander, and although he knows that this will put Ender through a lot of difficult situations, he says that, in the end, he will be Ender's friend.

Minor Characters

buggers
Little is known about them throughout the novel, even though they are presented as the threat to humankind. Because they are unable to communicate with humans, they are unable to explain the misunderstanding that resulted in them fighting against the humans in the previous two wars, and to avert the third one. Their home world is destroyed when Ender uses the device on it, but they create a landscape mimicking the one in the fantasy game in order to lead Ender to the hive queen, who explains the situation, leading to Ender's promise to find a new world for the buggers.

Mazer Rackham
Rackham had been the commander who had won the previous bugger war, by taking out the ship with the queen on it. The old man becomes Ender's teacher when he comes to Command School, and Ender believes it is him he is fighting on the simulator; Mazer is also the one who tells Ender after the war that this is not the case, that Ender has been fighting the buggers all along. He pilots the ship to the first colony on a bugger homeworld.

Stilson
Stilson is the bully at Ender's school at the start of the novel. He picks on Ender along with a group of other boys and when Ender talks him into fighting one-on-one, Ender kills him. Although the character is thus physically absent from the rest of the novel, Ender thinks about him throughout, as the first time he killed.

Battle School children (Alai, Bonzo, Petra, Dink, Bean, etc.)
The children at the Battle School are unlike typical children, in that they all feel the pressure of commanding in order to one day defeat the buggers. Alai is Ender's first and strongest friendship, Petra helps train him when he is not able to practice with the army, and Dink allows him to develop his skills at the game as well as warning him when he is in danger from Bonzo and his gang; Bean is similar to Ender, in that he is young and quite talented at the game. Most of his friends from Battle School end up fighting alongside Ender at Command School against the buggers, but the relationship of a commander to his subordinates remains strong.