Alex - The fifteen-year-old narrator and protagonist. Alex is the vicious leader of a gang of criminals who occasionally go to school by day and then rape and pillage by night. He loves classical music and finds that violence and music provide him with similar kinds of aesthetic pleasure. Alex believes that commitment to ideals—whatever those ideals might be—is of paramount importance, and he disdains people who seem to him to be living without purpose. Despite Alex’s brutality and his natural leadership potential, Alex remains quite naïve and immature, which allows him to be manipulated by both the government and F. Alexander’s political dissidents.

F. Alexander - A writer and political dissident. F. Alexander’s wife dies as a result of being raped by Alex’s gang. After his wife dies, he devotes his life to unseating the government that he holds partially responsible for his wife’s death. He is committed to the ideal of liberty, even at the expense of the individual. F. Alexander is a character foil for Alex, the protagonist, as well as a father figure to him.

Minister of the Interior -  A high-ranking government official who selects Alex as the first candidate for Ludovico’s Technique. The Minister is a sharply dressed, important-looking gentleman. His primary concern is the welfare of the State, and his attitude is entirely pragmatic.

Prison Chaplain -  The resident priest of Staja 84F, Alex’s prison. The chaplain (or charlie, in prison slang) is a big, burly drunk with a red face. He preaches to the prisoners about morals, but his career ambitions lead him to rationalize the treatment that Alex receives at the hands of the government. He gives the most concise expression of the importance of free will in the novel.

Dr. Brodsky - The State-employed behavioral scientist in charge of administering Ludovico’s Technique to Alex. Brodsky is short, fat, and hairy, with thick glasses and a rather sadistic temperament. He often laughs at Alex’s suffering. Unlike Alex, he knows nothing of classical music, except that it proves useful for intensifying Alex’s emotions during the administration of the technique. He also demonstrates a warped sense of morality by calling Alex “a true Christian” after Alex loses his ability to make his own moral choices.

Dr. Branom - Brodsky’s assistant. Branom is very happy in his work, bright-eyed and smiling all the time. His manner seems insincere and patronizing, since it persists even as he tortures Alex. Branom believes in science as if it were a religion, and he speaks reverently of its wonders.

Dim - A member of Alex’s gang who later becomes a police officer. Dim is the biggest, strongest, and stupidest member of Alex’s gang. He fights with a chain, and allows Alex to be captured by the police by incapacitating Alex by whipping him in the eyes. As a police officer, Dim is just as violent and thuggish as he was as a youth.

Pete - A member of Alex’s gang. Pete is mild-mannered and conciliatory. When Alex meets Pete again in Part Three, Pete has grown up and lives a simple life with his wife. His apparent satisfaction with this lifestyle leads Alex to want the same type of life for himself.

Georgie - A member of Alex’s gang. Georgie is the most ambitious of Alex’s first gang, and leads the rebellion against Alex. Unlike Alex, who is interested in violence for the pure sake of violence, Georgie is interested in violence for the sake of financial gain.

Billyboy - The leader of a rival teenage gang who later becomes a police officer. Billyboy is amazingly fat and fights with a knife. He is thinner when Alex meets him again in Part 3, but he is just as violent and thuggish as he was in his younger days.

Pee and em - Alex’s father and mother. Pee and em, are decent, ordinary people who sleepwalk their way through mundane existences in State jobs. They tolerate Alex’s unexplained comings and goings largely because they are timid and afraid of their son. Their shyness and weakness provide a foil to Alex’s vicious activism.

Z. Dolin, Rubinstein, and D. B. da Silva -  Political dissidents and associates of F. Alexander. These three, like F. Alexander, are greatly concerned with the cause of liberty. They think of their struggle against the State as a struggle for mankind, and they are largely willing to sacrifice individuals—in this case, Alex—for their cause.

P. R. Deltoid - Alex’s Post-Corrective Adviser, or Probation Officer. Deltoid is a tired and overworked public servant who labors at his job even as he grows increasingly aware of how little it actually helps. Alex confounds him because Alex’s violence does not share any characteristics with the typical explanations of human behavior to which Deltoid ascribes.

Jack - The old man from the library. Jack loves geometry and appears in Parts 1 and 3. When Alex’s gang finds him, he is carrying home books from the library on crystallography, snowflakes, and the rhombohedral system.

Joe - The lodger who lives in Alex’s room while Alex is incarcerated. Joe considers himself a son to Alex’s parents and hates Alex for the pain he has caused them.

Prison Governor -  The head of Staja 84F, Alex’s prison. Unlike the Minister of the Interior, the Governor believes that criminals should be punished the traditional way.

Chief Chasso - The head guard at Staja 84F. Volatile and mean, he despises the prisoners he watches and treats them mercilessly.

Rick, Len, and Bully -  Alex’s new gang in Part Three. These three are similar to Alex’s old gang from Part One, but they are more violent than the old gang and more fluent in nadsat.

The old woman, or the Catlady -  The old woman who dies as a result of Alex’s break-in. The old woman lives alone with her cats and seems crazy.

Marty and Sonietta -  Ten-year-old girls whom Alex rapes. These girls are typical youth who ditch school when they want, listen to pop music, and talk in their own slang. Alex finds them in the record store in Part One.

Rex - The police officer partnered with Dim and Billyboy. Rex is nonchalant when Billyboy and Dim beat Alex. He calmly sits in the car, reading a book and smoking a cigarette.

Andy - A record store employee. Andy is thin and bald and likes classical music. He sells Alex a copy of Beethoven’s Ninth Symphony in Part One.