Moreau was born in Paris on April 6,1826, the son of Louis Jean Marie Moreau, was an architect, who recognized his talent and his mother, Adele Pauline des Moutiers. Showing tremendous talent for drawing and painting in his youth, Moreau studied under Francois-Edouard Picot and became a friend of Master painter Théodore Chassériau (1819-1856), an eclectic painter whose depictions of enigmatic sea goddesses deeply impressed his student and strongly influenced his own work throughout his life.

Moreau was a reclusive artist who lived in almost total seclusion. He painted and drew constantly, often sacraficing sleep for days to work on his paintings. He lived and worked in his studio in Paris and carried on a deeply personal 25-year relationship, possibly romantic, with Adelaide-Alexandrine Dureux, a woman whom he drew and painted on more than one occasion. Though rarely seen as he was always in his studio he did exhibit his works in the Salon of 1853 and his painting "Oedipus and the Sphinx", one of his first symbolist paintings, was exhibited at the Salon of 1864.

He had become a professor at Paris' École des Beaux-Arts in 1891 and counted among his many students the fauvist painters, Henri Matisse, and Georges Rouault, Edgar Degas and Pierre Bonnaud. He continued to paint everyday and over his lifetime produced over 8,000 paintings and 12,800 drawings, many of which are on display in Paris' Musée national Gustave Moreau.

The museum is in his former workshop, and was opened to the public in 1903. André Breton famously used to "haunt" the museum and regarded Moreau as a precursor to Surrealism.

Moreau died in Paris in 1898 and was buried there in the Cimetière de Montmartre. He bequeathed his three-story house , containing more to the French state. His only wish was that the collection be kept together forever. "Taken as a whole," he stated, "they give an idea of what kind of an artist I was, and in what kind of surroundings I chose to live my dreams." More than a century later, Moreau's donation remains one of the most unusual attractions in Paris.