Born in Avalon in 1910, Gaston Chaissac is trained to several trades from a very young age before meeting  Otto Freundlich and Jeanne Kosnick-Kloss,  who initiated him to painting, in 1937, in Paris.

He first exhibition takes place in Paris in 1939. In 1942, he works at Saint-Rémy de Provence in a leather workshop ; he then meets several artists who encourage him, such as Albert Gleizes, André Lhote and Charles Mauron. In 1943, he settles with his family in Boulogne en Vendée. In 1943-1945, he participates in the Fair of the Independents, where he attracts the attention of Raymond Queneau, Jean Paulhan and Jean Dubuffet ; it is the beginning of a very abundant correspondence with them.

Dubuffet besides writes the foreword to his exhibition at the Arc- en- Ciel Gallery in 1947. In 1948, he settles at Sainte-Florence de l’Oie in Vendée, where his wife has been attached as a primary school teacher. In 1951, Hippobosque au Bocage is published by Gallimard, a collection of letters and poems edited by Jean Dubuffet. From 1958 to 1960, he regularly collaborates to the new NRF, while living more and more isolated in a area where he wins but sarcasms. However, the year of his settling in Vix, in 1961, is the year when he gains recognization as a painter in Paris, at the Iris Clert Gallery. He dies three years later in 1964, at the La Roche- sur -Yon Hospital, in the same destitution he had known all his life.

The National Museum of Modern Art honours him with a retrospective which definitely establishes him , ten years after his death, as one of the most important artists of his time. Two other major retrospectives were also devoted to him, one at the Fine Arts Museum in Nantes in 1998 and the other at the National Gallery of the Jeu de Paume in 2000.