Augustin Lesage was born in Saint-Pierre-lez-Auchel on August 9, 1876. Coming from a family of miners, Lesage followed in their father's footsteps and took up the trade immediately after finishing primary school, and he married a miner's daughter. He had never shown any aptitude for drawing, and his only contact with the arts was a visit to the Palais des Beaux-Arts in Lille during his military service.

In 1911, while working underground, he heard a voice tell him, "One day, you will be a painter." A few months later, he was introduced to spiritualism by fellow miners and demonstrated exceptional mediumistic abilities. According to his account to Dr. Osty, Lesage said that spirits commanded him to draw and then to paint. After beginning his first automatic drawings, the spirit dictated to him, "Today, it's no longer a question of drawing, but of paintings." Have no fear, and follow our advice carefully. Yes, one day you will be a painter, and your paintings will be subjected to scientific scrutiny. You will find this ridiculous at first. We will guide your hand. Do not try to understand. Above all, follow our advice carefully.

He was then mobilized for the war between 1914 and 1916. At the end of the war, he was reassigned to the coal mines and he also took up painting again, continuing to paint until his death.

In 1921, he received a visit from Jean Meyer, director of La Revue spirite. Meyer quickly became his patron, which allowed Augustin Lesage to leave the mine for good in 1923. His painting was exhibited in 1927 at the Metapsychic Institute of Paris for several months, and people were astonished, according to Dr. Osty, "that an uneducated man, without artistic heritage, a simple miner, could have achieved this form of art." »

Associated with the spiritualist movement, and cited by André Breton in the surrealist journal Le Minotaure in 1933, he is included in the Collection de l'Art Brut, of which he is a major figure.