Alexander Friedrich Wilhelm Duncker (Feb. 18, 1813 – Aug. 23, 1879) was a German publisher and bookseller.
He was descended from a successful Berlin family of booksellers, born in Berlin, the son of Carl Friedrich Wilhelm Duncker (1781–1869) and Fanny Duncker (née Wolff). His brothers included historian and politician Maximilian Duncker (1811–1886), and publisher and pundit Franz Duncker (1822–1888), founder of a trade union with labor economist Max Hirsch (1832–1905). Another brother, Hermann Carl Rudolf Duncker (1817–1892) was a member of the Prussian National Assembly and a mayor of Berlin.
Duncker's father had founded the publishing firm Duncker & Humblot in 1809, running it alone after business partner Peter Humblot died in 1828. Alexander Duncker started his education in 1829. After apprenticeships with Friedrich Christoph Perthes and Johann Besser in Hamburg, Duncker founded his own firm, "Verlag Alexander Duncker." His firm specialized in Belles lettres (German: Belletristik) and visual arts. Among the authors he published were Thekla von Gumpert, Ida Hahn-Hahn, Paul Heyse, Karl von Holtei, August Kopisch, Fanny Lewald, Elise Polko, Christian Friedrich Scherenberg, Hermann von Pückler-Muskau, and Friedrich von Uechtriz. He was instrumental in promoting new authors, and some of them Emanuel Geibel, Wilhelm Jensen, Marie Petersen, Gustav zu Putlitz, and Theodor Storm found their first recognition through Duncker's efforts.