Ludwig-Friedrich Bonnet de Saint-Germain, FRS (12 December 1670, 1893 – 7 April 1761) was a Swiss physician, lawyer, scholar, and politician. He was also a diplomat in the service of Prussia. He was born in Geneva in 1670, into a family of French Protestants (Huguenots) from Provence, who had fled to Switzerland during the French Wars of Religion and married there into the family of the eminent German Calvinist theologian Friedrich Spanheim. Ludwig-Friedrich Bonnet studied medicine at Leiden University. Both him and his older brother Frédéric then followed their uncle Ezekiel von Spanheim into the diplomatic service of the government of Prussia (officially Brandenburg-Prussia until 1701, afterwards the Kingdom of Prussia). Posted to England, he was known there as Louis Frederick Bonet.