César-François Cassini de Thury

César-François Cassini de Thury (1714–1784), known as Cassini III, was a French astronomer and cartographer. Born at Thury-sous-Clermont, he was the second son of Jacques Cassini and grandson of Giovanni Domenico Cassini, founder of the Paris Observatory. He entered the Academy of Sciences in 1739.

In 1744 he began a trigonometric survey of France, which produced the 180-sheet Cassini map, the kingdom's first complete topographical map, completed by his son in 1793. Appointed the Paris Observatory's first director in 1771, he proposed a survey linking it with the Greenwich observatory and died of smallpox in 1784.