French tax-farmer of the fourteenth century. With Manecier of Vesoul and his brother Vivant he was appointed (1360) by Charles V., King of France, to collect the taxes imposed upon the Jews, retaining two florins out of the fourteen which each Jew had to pay upon entering France. In 1365 a dispute arose between Jacob and Manecier, in consequence of which the former brought suit against his opponent before the parliament of Paris, and Manecier was fined. The two functionaries became reconciled in 1370, and their position with the king, although weakened, was still sufficiently important to enable them at the approach of Passover in 1372 to obtain the loan of the Hebrew books deposited in the Sainte Chapelle, Paris.