Born to a poor Jewish family in Dessau, Principality of Anhalt, and originally destined for a rabbinical career, Mendelssohn educated himself in German thought and literature and from his writings on philosophy and religion came to be regarded as a leading cultural figure of his time by both Christian and Jewish inhabitants of German-speaking Europe and beyond. He also established himself as an important figure in the Berlin textile industry, which was the foundation of his family's wealth.
His descendants include the composers Fanny and Felix Mendelssohn; Felix's son, chemist Paul Mendelssohn Bartholdy; Fanny's grandsons, Paul and Kurt Hensel; and the founders of the Mendelssohn & Co. banking house.
Moses Mendelssohn was born in Dessau. His father's name was Mendel, and it was Moses who adopted the surname Mendelssohn ("Mendel's son"). Moses's son Abraham Mendelssohn wrote in 1829 (to Felix), "My father felt that the name Moses Ben Mendel Dessau would handicap him in gaining the needed access to those who had the better education at their disposal. Without any fear that his own father would take offense, my father assumed the name Mendelssohn. The change, though a small one, was decisive."
Mendel was an impoverished scribe — a writer of Torah scrolls — and his son Moses in his boyhood developed curvature of the spine. Moses's early education was cared for by his father and by the local rabbi, David Fränkel, who besides teaching him the Bible and Talmud, introduced to him the philosophy of Maimonides. Fränkel received a call to Berlin in 1743. A few months later Moses followed him.
A refugee Pole, Israel Zamosc, taught him mathematics, and a young Jewish physician taught him Latin. He was, however, mainly self-taught. He learned to spell and to philosophize at the same time (according to the historian Graetz). With his scanty earnings he bought a Latin copy of John Locke's An Essay Concerning Human Understanding, and mastered it with the aid of a Latin dictionary. He then made the acquaintance of Aaron Solomon Gumperz, who taught him basic French and English. In 1750, a wealthy silk-merchant, Isaac Bernhard, appointed him to teach his children. Mendelssohn soon won the confidence of Bernhard, who made the young student successively his bookkeeper and his partner.