John Forbes Nash Jr. - John Nash (1928-2015) was an American mathematician and Nobel Prize Laureate in Economics. The book covers his life from childhood through his groundbreaking work in game theory at Princeton, his struggle with schizophrenia, and his later life and Nobel Prize win in 1994.

Alicia Larde (Alicia Nash) - Alicia is John Nash's wife, whom he met while working as an instructor at MIT. She is described as an undergraduate student studying physics. The book details their marriage and her support of Nash through his mental illness.

Eleanor Stier - Eleanor Stier was a nurse that Nash had a relationship with in 1952, resulting in the birth of their son John David Stier. Nash was unmarried to Stier at the time.

Other Characters
Martha Nash Legg - Nash's younger sister, described as "tall and striking" and "extremely intelligent"
John David Stier - Nash's son with Eleanor Stier, born in 1953.