Abraham Ernst Mendelssohn Bartholdy (born Abraham Mendelssohn; 10 December 1776 – 19 November 1835) was a German banker and philanthropist. He was the father of Felix Mendelssohn and Fanny Mendelssohn.
Mendelssohn was born and died in Berlin. The son of the philosopher Moses Mendelssohn, Abraham is supposed to have complained to a friend, "Once I was the son of a famous father, now I am the father of a famous son."
By the time of Moses's death in 1786 the Mendelssohn family was well established and wealthy. In line with Moses's ideas that German Jews should participate in German as well as Jewish culture Abraham had a liberal education. He was one of the founding members of the Jewish liberal society Gesellschaft der Freunde in 1792, but also of the Sing-Akademie zu Berlin founded in 1793. In 1796 his future wife Lea Salomon, a granddaughter of Daniel Itzig, also joined the Akademie; but they had probably met before that.
In 1797 Abraham went to study banking in Paris at the behest of his brother Joseph, who had formed the banking house of Mendelssohn and Friedlaender in association with Daniel Itzig's grandson, Moses Friedlander. French life did not appeal to him. In 1804 Abraham married Lea in Hamburg, where he managed an office of the family bank. Somewhere around this time he seems to have acquired from Lea's acquaintance with the musician Georg Poelchau a number of manuscripts of C. P. E. Bach (of whom Poelchau was the executor), which he gave to his aunt, the musician Sara Levy, who subsequently donated them to the Singakademie.
In 1804, Abraham Mendelssohn became a partner in his brother Joseph's banking company. The cooperation lasted until 1822. The private bank which later was renamed into Mendelssohn & Co., existed on the Jägerstraße in Berlin from 1815 until the end of 1938, when it was liquidated under Nazi pressure.