The novel begins with Lord Henry Wotton, observing the artist Basil Hallward painting the portrait of a handsome young man named Dorian Gray. Dorian arrives later, meeting Wotton. After hearing Lord Henry's world view, Dorian begins to think beauty is the only worthwhile aspect of life, the only thing left to pursue. He wishes that the portrait of himself which Basil is painting would grow old in his place. Under the influence of Lord Henry, Dorian begins to explore his senses. He discovers actress, Sibyl Vane, who performs Shakespeare in a dingy theatre. Dorian approaches her and soon proposes marriage. Sibyl, who refers to him as "Prince Charming," rushes home to tell her skeptical mother and brother. Her protective brother, James, tells her that if "Prince Charming" harms her, he will kill him.
Dorian invites Basil and Lord Henry to see Sibyl perform in Romeo and Juliet. Sibyl, whose only knowledge of love was love of theatre, loses her acting abilities through the experience of true love with Dorian. Dorian rejects her, saying her beauty was in her art, and he is no longer interested in her if she can no longer act. When he returns home he notices that Basil's portrait of him has changed. Dorian realises his wish has come true – the portrait now bears a subtle sneer and will age with each sin he commits, whilst his own appearance remains unchanged. He decides to reconcile with Sibyl, but Lord Henry arrives in the morning to say Sibyl has killed herself by swallowing prussic acid (hydrogen cyanide). With the persuasion and encouragement of Lord Henry, Dorian realizes that lust and looks are where his life is headed and he needs nothing else. That marked the end of Dorian's last and only true love affair. Over the next 18 years, Dorian experiments with every vice, mostly under the influence of a "poisonous" French novel, a present from Lord Henry. Wilde never reveals the title but his inspiration was possibly drawn from Joris-Karl Huysmans's À rebours (Against Nature) due to the likenesses that exist between the two novels.
One night, before he leaves for Paris, Basil arrives to question Dorian about rumours of his indulgences. Dorian does not deny his debauchery. He takes Basil to the portrait, which is as hideous as Dorian's sins. In anger, Dorian blames the artist for his fate and stabs Basil to death. He then blackmails an old friend named Alan Campbell, who is a chemist, into destroying Basil's body. Wishing to escape his crime, Dorian travels to an opium den. James Vane is nearby and hears someone refer to Dorian as "Prince Charming." He follows Dorian outside and attempts to shoot him, but he is deceived when Dorian asks James to look at him in the light, saying he is too young to have been involved with Sibyl 18 years earlier. James releases Dorian but is approached by a woman from the opium den who chastises him for not killing Dorian and tells him Dorian has not aged for 18 years.
While at dinner, Dorian sees Sibyl Vane's brother stalking the grounds and fears for his life. However, during a game-shooting party a few days later, a lurking James is accidentally shot and killed by one of the hunters. After returning to London, Dorian informs Lord Henry that he will be good from now on, and has started by not breaking the heart of his latest innocent conquest, a vicar's daughter in a country town, named Hetty Merton. At his apartment, Dorian wonders if the portrait has begun to change back, losing its senile, sinful appearance, now he has changed his immoral ways. He unveils the portrait to find it has become worse. Seeing this, he questions the motives behind his "mercy," whether it was merely vanity, curiosity, or the quest for new emotional excess. Deciding that only full confession will absolve him, but lacking feelings of guilt and fearing the consequences, he decides to destroy the last vestige of his conscience. In a rage, he picks up the knife that killed Basil Hallward and plunges it into the painting. His servants hear a cry from inside the locked room and send for the police. They find Dorian's body, stabbed in the heart and suddenly aged, withered and horrible. It is only through the rings on his hand that the corpse can be identified. Beside him, however, the portrait has reverted to its original form.