Fanny Lewald (21 March 1811–5 August 1889) was a German author.

She was born at Königsberg in East Prussia. Lewald was born Jewish, and when seventeen years of age, she converted to Christianity. She traveled in the German Confederation, France and Italy. Travel developed her powers of composition, and in 1841 she published her first novel in her cousin August Lewald's periodical Europa, under the title Der Stellvertreter. In 1845, she settled at Berlin. Here, in 1854, she married the author Adolf Stahr. In 1876, after his death, she moved to Dresden, where she engaged in literary work until her death in 1889.

Lewald is less remarkable for her writings, which, though displaying considerable talent and culture, are mostly sober, matter-of-fact works, than for her championship of women's rights and for her scathing satire on the sentimentalism of the Gräfin von Hahn-Hahn. This author she ruthlessly attacked in the exquisite parody Diogena, Roman von Iduna Gräfin H...-H... (2nd ed., 1847).