This paper analyzes and investigates oneiric art throughout history by studying five iconic artists—Hieronymus Bosch, William Blake, Francisco de Goya, Odilon Redon and Salvador Dalí—and their works in depth, discovering the evolution of the theme *Dream*. The theme is put in different contexts—both Eastern and Western—and focuses on Western art from the Renaissance to the Avant-gardes in the 20th century. The techniques applied, art styles, artistic intentions and the lives of the artists are also explored. Dreams have been a source of inspiration throughout human history. In Western Art History, oneiric art is usually associated with mythology, religion and allegory. The Romantic movement pushed forward the development of oneiric art, followed by Symbolism and Surrealism in the 20th century. Specifically, Bosch's *The Garden of Earthly Delights* depicts original sin and punishment through grotesque and surreal imagery, while Blake's *Jacob's Ladder* conveys a mystical religious vision through a unique spiral staircase composition.This paper analyzes and investigates oneiric art throughout history by studying five iconic artists—Hieronymus Bosch, William Blake, Francisco de Goya, Odilon Redon and Salvador Dalí—and their works in depth, discovering the evolution of the theme *Dream*. The theme is put in different contexts—both Eastern and Western—and focuses on Western art from the Renaissance to the Avant-gardes in the 20th century. The techniques applied, art styles, artistic intentions and the lives of the artists are also explored. Dreams have been a source of inspiration throughout human history. In Western Art History, oneiric art is usually associated with mythology, religion and allegory. The Romantic movement pushed forward the development of oneiric art, followed by Symbolism and Surrealism in the 20th century. Specifically, Bosch's *The Garden of Earthly Delights* depicts original sin and punishment through grotesque and surreal imagery, while Blake's *Jacob's Ladder* conveys a mystical religious vision through a unique spiral staircase composition.