Nathanael
The main character of The Sandman. Nathanael was obsessively afraid of The Sandman as a child, though he wasn't sure whether he was afraid of a man or monster. As a young man, he is still afraid of this figure, having now settled on the double of Coppelius/Coppola, which he believes to be The Sandman. He is engaged to Clara, but falls in love with Olimpia, whom he ultimately realizes she is a doll.
Lothar
The brother of Nathanael's fiancée, Clara, and Nathanael's close friend himself, Lothar is the person to whom Nathanael first reveals his obsession with The Sandman. Lothar is a man of calm logic, and attempts to convince Nathanael that his fears are merely childish imagination spilling over into his adult life.
Clara
Clara is Nathanael's fiancée and once was his close childhood friend. She is described as having "womanly calm and deliberation," and her relationship with Nathanael is quite unbalanced by his obsession with The Sandman, as well as the abrupt onset of his love for Olimpia.
Coppelius/Coppola/The Sandman
Coppelius is a man who often visited Nathanael's family, especially his father, when Nathanael was a child. Nathanael believes him to be The Sandman, and also believes that the mechanic named Coppola, whom he meets while at university, is the man from his childhood in disguise. These characters merge into one another throughout the story, becoming more-or-less the same person. However, after the reveal of Olimpia as a wooden doll full of machinery, and due to Coppola's obsessive focus on her eyes, it can be guessed that Hoffmann intends the characters to be truly viewed as one and the same.
Professor Spalanzani
A professor at Nathanael's university and "father" of Olimpia, who turns out to have been working with Coppola to produce her and fool others in society.
Olimpia
The lifelike doll, created by Professor Spalanzani and Coppola, with which Nathanael falls in love at university.
Nathanael's father
Nathanael's father died when Nathanael was a child, but he is the reason Nathanael is introduced to Coppelius through their apparent mutual involvement in an alchemy project.
Siegmund
Siegmund is Nathanael's friend from university, who attempts to reason with him regarding Olimpia after the ball, and comes to his aid after the fight over Olimpia in Spalanzani's house, seeing him taken safely to the madhouse.
