The son of émigré Italian scholar Gabriele Pasquale Giuseppe Rossetti and his wife Frances Polidori, Rossetti was born in London, and named Gabriel Charles Dante Rossetti. His family and friends called him Gabriel, but in publications he put the name Dante first (in honour of Dante Alighieri). He was the brother of poet Christina Rossetti, critic William Michael Rossetti, and author Maria Francesca Rossetti. During his childhood, Rossetti was home educated and often read the Bible, along with the works of Shakespeare, Dickens, Sir Walter Scott and Lord Byron.
The young Rossetti is described as "self-possessed, articulate, passionate and charismatic" but also "ardent, poetic and feckless". Like all his siblings, he aspired to be a poet and attended King's College School, in its original location near the Strand. He also wished to be a painter, having shown a great interest in Medieval Italian art. He studied at Henry Sass's Drawing Academy from 1841 to 1845 when he enrolled at the Antique School of the Royal Academy, leaving in 1848. After leaving the Royal Academy, Rossetti studied under Ford Madox Brown, with whom he retained a close relationship throughout his life.
Following the exhibition of William Holman Hunt's painting The Eve of St. Agnes, Rossetti sought out Hunt's friendship. The painting illustrated a poem by the little-known John Keats. Rossetti's own poem, "The Blessed Damozel", was an imitation of Keats, and he believed Hunt might share his artistic and literary ideals. Together they developed the philosophy of the Pre-Raphaelite Brotherhood which they founded along with John Everett Millais.
The group's intention was to reform English art by rejecting what they considered to be the mechanistic approach first adopted by the Mannerist artists who succeeded Raphael and Michelangelo and the formal training regime introduced by Sir Joshua Reynolds. Their approach was to return to the abundant detail, intense colours, and complex compositions of Quattrocento Italian and Flemish art. The eminent critic John Ruskin wrote:
Every Pre-Raphaelite landscape background is painted to the last touch, in the open air, from the thing itself. Every Pre-Raphaelite figure, however studied in expression, is a true portrait of some living person.
For the first issue of the brotherhood's magazine, The Germ, published early in 1850, Rossetti contributed a poem, "The Blessed Damozel", and a story about a fictional early Italian artist inspired by a vision of a woman who bids him combine the human and the divine in his art. Rossetti was always more interested in the medieval than in the modern side of the movement, working on translations of Dante and other medieval Italian poets, and adopting the stylistic characteristics of the early Italians.