Pierre Rousseau (1905-1983) was a French astronomer, science journalist, and essayist, one of the major French science popularizers of the twentieth century. Born on 11 February 1905 in Montbazon (Indre-et-Loire), educated at the Sorbonne (philosophy degree 1935, mathematical and physical sciences degree) and the Meudon Observatory, he published his first book, L'Exploration du ciel, with Hachette in 1939. His prolific output spans astronomy, epistemology (Histoire de la science, 1945), geology, nuclear physics (Histoire de l'atome, 1948), and astronautics (Satellites artificiels, 1957). From 1945 he directed Fayard's "Savoir" series, in which several reference treatises for educated readers appeared, including Alexandre Ananoff's L'Astronautique (1950), to which he contributed the preface. He died in 1983 in Limeil-Brévannes.