Frankenstein's monster (sometimes Frankenstein's cCreature or the Frankenstein monster) is a creature first appearing in Mary Shelley's novel, Frankenstein, or The Modern Prometheus. The popular names for the monster were not established until after the novel's publication; in the novel, he is usually referred to as "the creature," "the fiend," or "the wretch." Frankenstein's monster is also commonly but incorrectly referred simply as "Frankenstein," since the monster had no name.

Template:Spoiler In the novel, Victor Frankenstein builds the creature through methods of science and/or alchemy which are not clearly described. Immediately upon bringing the creature to life, however, Frankenstein flees from it in horror and disavows his experiment. Abandoned, frightened, and completely unaware of who or what he is, the Creature wanders through the wildnerness searching for someone who would understand and shelter him.

He finds brief solace by hiding out in the wood shed of a remote cabin inhabited by a large family. While they are unaware of his existence, he learns every part of their lives by eavesdropping on their conversations; he comes to think of them as his own family. He develops the power of speech from listening to the family teach their language to an Arabian daughter-in-law, and very quickly becomes eloquent and well-mannered.

One day, he musters the courage to finally make his presence known. He introduces himself to the family's patriarch, their blind grandfather, and experiences kindness and acceptance for the first (and last) time, as the blind man can not see his "accursed ugliness," and so treats him as a friend. When the rest of the family returns, however, they are terrified of him and drive him away. Heartbroken, he renounces all of mankind and swears revenge on his creator, Frankenstein, for bringing him into the world.

The creature searches for Frankenstein relentlessly, guided by some papers which were in the pocket of the clothing he took from his creator's rooms. Upon arriving near Frankenstein's home town, he meets and tries to befriend a small boy, hoping that the innocent youth will not be prejudiced against him. The boy is instantly frightened and threatens to get his father—Monsieur Frankenstein—and thus the creature learns that the boy is related to his enemy. The creature kills him, and, in a further gesture of hatred against humanity, frames the murder on a girl sleeping nearby by pinning a locket on her person. The girl happens to be the Frankenstein family maid. She goes to the gallows because Frankenstein decides it would be futile to confess his experiment, as no one would believe him.

Intent on his own revenge, Frankenstein hunts the creature, and finds him in a remote ice cave. Here the creature tells Frankenstein his story and pleads with him to create a female creature so he can flee from humanity with one of his own kind. Frankenstein agrees, but relents just before finishing the mate, aghast at the possibility of creating a race of monsters. Enraged, the creature swears he will destroy everything Frankenstein holds dear.

He makes good on his promise on Frankenstein's wedding night by killing his bride and his best friend. With nothing left to live for, Frankenstein dedicates his life to hunting down and destroying the creature. He scours the country obsessively, unaware that his creation is stalking his every move. The search ends in the Arctic Circle when Frankenstein loses control of his dogsled and falls into ice cold water, contracting severe pneumonia. He is rescued by a ship exploring the region, and relates the entire story to its captain, Walton, before succumbing to his illness and dying. The creature boards the ship intent on taking his final revenge, but is overcome with grief and remorse upon finding Frankenstein dead, having lost the only family he has ever known. He pledges to travel to "the Northernmost extremity of the globe," and there commit suicide.

Few details of the creature's physical appearance are given in the original novel, except that he is about eight feet in height, has yellowish skin and eyes and flowing black hair, and is hideous.

The image of Frankenstein's monster in popular culture comes mostly from Boris Karloff's portrayal in the 1931 movie Frankenstein, as a lumbering, flat-headed giant with bolts through the neck. Further interpretations have added green skin (Because of Karloff's makeup, which was green so that it'd show up better on the black and white film) and a characteristic scar across the forehead.

The monster and characters based upon him have starred in a number of movies, comic books, television shows, cartoons, and virtually every form of media and art—sometimes symbolically, other times as satire. He has been portrayed by a number of actors, Karloff being the most famous. Of all the actors who have played him, critics have cited Robert De Niro's performance in Mary Shelley's Frankenstein as arguably the most faithful.

The creature has often been portrayed as representing various social, environmental, and psychological themes. Interpretations he has been attributed to include the danger of man playing God and the dangers of toying with what you do not understand. This interpretation could possibly be of merit, as the novel was written just at the beginning of the Industrial Revolution, the critics of which claimed that scientists and businessmen were using the natural world in perverse, destructive ways. He has also been cited as a metaphor for personal responsibility; Victor Frankenstein errs in giving the creature life without consideration for the consequences, and is destroyed by his refusal to acknowledge and deal with his mistake.

• Lisa of Weird Science was a sort of computer-generated Frankenstein monster, designed to be a toy for Gary and Wyatt. Though not technically undead, the method of her creation and her rebellious nature make constant references to the Frankenstein's monster. There is even an episode of the television show where Gary and Wyatt match their creation Lisa against Frakenstein's monster to see who has created the superior being.
• Herman Munster of The Munsters looks almost identical to Boris Karloff's interpretation.
• The Incredible Hulk, a popular superhero character and comic book series, was partially inspired by Frankenstein. He not only looks much like the typical version of Frankenstein's monster, but also acts in a similarly brutish, volatile manner.
• Franken Berry, a cereal and its mascot, are named after the character. Its appearance is similar to his but noticably altered.