Sophie Fevvers
Fevvers is the protagonist and hero of Nights at the Circus. She was allegedly hatched from an egg and left on the stoop of Ma Nelson's brothel as a hatchling. From there, she was taken in by Lizzie and raised among the women at the brothel. She has wings, which fully spread during her adolescence. By the start of the novel, she's made a name for herself as a celebrity aerialist and trapeze artist. She travels with the Grand Imperial Circus and is quite an imposing presence, standing at over six feet tall with a wingspan of more than twice that.
Lizzie
Lizzie is the housekeeper at Ma Nelson's brothel where Fevvers was raised. She connects with Fevvers because she'd lost her baby just before infant Fevvers was left on the stoop, and so she adopts Fevvers as her own, nurses her, and raises her. The two form a bond and are always together. In addition to being a fierce protector and advocate for Fevvers, Lizzie works with resistance groups around the world to advance humanitarian causes and end subjugation and tyranny.
Jack Walser
Jack Walser is a young journalist from San Francisco who interviews Fevvers in an attempt to expose her as a fake. Her personality intrigues him and he falls in love with her. He joins the circus as an undercover clown, supposedly to write about the experience, but really to be near Fevvers. On the way to Siberia, he's left being in the rubble of the train wreck and is taken in by a Siberian shaman, who trains him in the ways of shamanism.
Ma "Admiral" Nelson
Ma Nelson is the beloved matriarch of the brothel where Fevvers is raised. Fevvers stays there until Ma Nelson’s untimely death. She leaves Fevvers her admiral's sword, to make her look like Winged Victory, and the sword makes Fevvers feel invincible.
Madame Schreck
Madame Schreck runs what she calls a "museum of women monsters." She keeps women with unusual attributes, some of whom would be hired by "freak shows" in traveling circuses, locked in her dungeon, and charges men admission to observe them. Most of the women she keeps as sex slaves for her clients, but Fevvers maintains that she and Sleeping Beauty, one of the other prisoners of Schreck, were only kept for observation. Madame Schreck sells Fevvers to a wicked man named Christian Rosencreutz, and in response, Fevvers flies her to the ceiling of her dungeon and hangs her from a chandelier, where she turns to dust.
Christian Rosencreutz
Christian Rosencreutz is a Rosicrucian occultist who believes that Fevvers is an angel of death. He purchases her from Madame Schreck for the purpose of ritualistically sacrificing her, with the hope that by doing so, he can become immortal.
Colonel Kearny
Colonel Kearny is an American businessman who hires Fevvers for his Grand Imperial Circus that travels across Russia into Japan. He takes pride in doing that which no circus has done before, traveling further and wider than even the great generals of antiquity. Like Fevvers, he will do virtually anything for money and fame, and he's driven in large part by greed. He tells lies about his performers to get publicity for the circus, and the creature he cares most about in the world is his beloved pet, partner, and confidante: his teacup pig, Sybil.
Sybil
Sybil is a small pig that Colonel Kearny believes is clairvoyant. He consults her on every business decision he makes. Sybil is the granddaughter of Colonel Kearney's original pet pig, also named Sybil, who was the first act of his circus (as a young man, he trained her to stand on her hind legs and wave the American flag).
Mignon
Mignon is introduced as the girlfriend of Monsieur Lamarck, Kearney's ape-trainer. Mignon is the daughter of a bread-maker who killed his wife, Mignon's mother, when he found out she was cheating on him with officers stationed near their home. Mignon runs from the orphanage and, for a time, works for a scam artist who convinces families that he can commune with their deceased daughters. Then Mignon eventually runs away with Lamarck and the circus, but Lamarck abuses her. When she meets Walser and Fevvers, she's introduced to the Princess of Abyssinia, and they fall in love and develop a duet act together, in which Mignon sings and the Princess plays piano.
The Professor
The Professor is an ape who is highly intelligent. He has to lead the act because Monsieur Lamarck is too busy drinking to direct. The Professor negotiates a new contract with Colonel Kearney to officially take charge of the act, and this new contract includes a clause that allows the apes to leave the circus after the show in St. Petersburg.
Buffo the Great
Buffo the Great is a veteran clown and the leader of clowns in Colonel Kearney's Grand Imperial Circus. He is often compared to Jesus Christ, and his main acts include a "Christmas Dinner" routine, which is staged like the Last Supper, and a resurrection routine. Buffo is a high-functioning alcoholic, until the last night in Petersburg, when he gets so drunk that he ceases to function, tries to kill Walser mid-performance, and is carted off to a mental hospital.
The Charivaris
The Charivaris are a family of acrobats in Colonel Kearney’s circus. They were the top-billed act until Fevvers was hired into the circus. The family has performed for tsars, kings, and emperors, and they resent being second to Fevvers. This leads them to sabotage Fevvers' act out of jealousy, but their sabotage fails, and they are fired from the circus.
The Brotherhood of Free Men
The brotherhood of free men are men who have been exiled to Siberia for minor crimes. They are desperate to return to their families so they cause the train wreck to the circus train. They read the false story that Fevvers is engaged to the Prince of Wales and believe that she can get their story to the Queen of England, who will have the power to pardon them and reunite them with their families.
Olga Alexandrovna
Olga Alexandrovna is an escapee from an experimental women's prison in Siberia. She helps after the train wreck. She nurses Walser and keeps him safe. The escapees from the prison and the guards set up a republic for women in the Siberian wilderness. This is a place where they can be free from the rule of men.
The Shaman
The shaman is a healer in the Siberian wilderness. He finds Walser wandering in the Siberian woods and takes him under his wing. Mistaking Walser's amnesia and English babble for the behavior of someone with access to the ancestral plane, the shaman trains Walser in the ways of shamanism. The shaman shares characteristics with Fevvers, such as a charismatic flair and talent for prestidigitation.
The Maestro
The Maestro has a conservatory in the middle of Siberia. He was tricked into coming to the remote wilderness by a corrupt mayor and is miserable and isolated. He forms a bond with the Princess of Abyssinia when she and the other survivors of the train wreck find his conservatory. The Princess tunes his piano, and together with Mignon, the three musicians begin to make music together.
