Called Gaspard Poussin and Le Guaspre; born on 4 June 1615 in Rome, the son of a French cook, Jacques Dughet, and his Italian wife. In 1630 his elder sister married Nicolas Poussin with whom he studied landscape painting 1631-4, their close relationship leading to his being called Gaspard Poussin. In 1635 he went to Milan and Perugia and sometime in 1641-6 he was in Florence and Naples, but his life was otherwise spent in and around Rome.

His earliest biographers described him as fond of hunting and fishing, and from c. 1635 he had lodgings at Frascati and Tivoli. Although he evidently studied the landscapes of Titian, Claude, Cortona, Domenichino and, above all, Poussin, his own were distinguished by a degree of naturalism and the comparative insignificance of his figures. His first major public commission was for a cycle of landscape frescoes in the church of S. Martino ai Monti, Rome, in 1647-51; he received several fresco commissions, the last for the Palazzo Colonna in 1667-8.

His reputation as a landscape painter was rivalled in his lifetime only by those of Claude Gellée and Salvator Rosa, and he was received into the Accademia di S. Luca in 1657. He died in Rome, after a long illness, on 25 May 1675. His influence on subsequent landscape painting was profound, and nowhere more than in England in the eighteenth century.