Born on 14 April 1724 in Paris, one of fourteen children of the engraver Gabriel-Germain de Saint-Aubin under whom he first studied. The entire family was involved in the arts, and Gabriel’s older brother, Charles-Germain, was an important artist in his own right, as well as Gabriel’s biographer and one of his earliest artistic influences. Exact dates for many of Gabriel's activities are lacking, but there are some landmarks. Gabriel was mentored at the Académie royale with François Boucher, Étienne Jeurat (1699-1789) and Hyacinthe Collin de Vermont (1693-1761). He made three unsuccessful attempts – in 1752, 1753, and 1754 – to win the Grand prix, but was still a student at the Académie royale in 1758. He taught at Jacques-François Blondel’s École des Arts, where he is mentioned in 1747, and he was also a member of and teacher at the Académie de Saint-Luc. We know of only two exhibitions in which Gabriel participated during his lifetime, one in 1774 at the Académie de Saint-Luc, the other in 1776 at the Colisée. He died in absolute poverty in Charles-Germain’s home in 1780.
Saint-Aubin is best known to us today as a draughtsman. He does not seem to have been a prolific painter. Charles-Germain lists some 4 to 5000 unfinished drawings in Gabriel’s studio after his death. He walked, according to all accounts, tirelessly the streets of Paris and drew everything in sight. We have approximately 1000 of those drawings today, and they form an incomparable view of many aspects of eighteenth-century life in Paris. Among the most famous of his drawings are the tiny marginal sketches of exhibited art works in the catalogues of the Salon exhibitions.