Moreau produced over fifteen thousand works and converted his own house into a museum to hold them. When he died in 1898, the building at 14 rue de la Rochefoucauld in Paris became the Musee Gustave Moreau, exactly as he had planned. Eight thousand paintings, watercolours and drawings hung floor to ceiling in the rooms where he had lived and worked.

He was born in Paris in 1826, a sickly, solitary child who drew compulsively. He trained at the Ecole des Beaux-Arts and fell under the influence of Theodore Chasseriau, an eclectic painter whose depictions of enigmatic sea goddesses left a permanent mark. Chasseriau's death in 1856 shook Moreau badly enough to send him to Italy for two years, where he copied Mantegna, Carpaccio and the Venetians, filling notebooks with studies that fed his work for decades.

His breakthrough came at the 1864 Salon with Oedipus and the Sphinx, a painting that fused classical mythology with a strange, jewelled intensity that critics struggled to categorise. He became the foremost Symbolist painter, working in a style guided by what has been called Neo-Platonist faith: a belief that the physical world was imperfect and that art could capture something closer to divine vision. He never married, regarding the career of an artist as "a true priesthood", though he maintained a discreet relationship with Alexandrine Dureux for decades, subsidising an apartment for her near his family home.

As a teacher at the Ecole des Beaux-Arts, Moreau proved unexpectedly open-minded. His students included Henri Matisse and Georges Rouault, both of whom credited his insistence on personal expression over academic formula. Andre Breton and Salvador Dali later claimed his Symbolist imagery as a direct precursor to Surrealism.