Alexander Saeltzer (*1814 Eisenach, Saxe-Weimar-Eisenach, Germany — 23 September 1883 New York City) was a German-American architect active in New York City in the 1850s and 1860s. His work includes the Anshe Chesed Synagogue (now the Angel Orensanz Center), Academy of Music (New York City), Theatre Francais (New York), the Duncan, Sherman & Company building and the South Wing of the Romanesque revival structure at 425 Lafayette Street built between 1853 and 1881 as the Astor Library (which later merged with the Tilden and Lenox collections to become the New York Public Library).
His father, Wilhelm Saeltzer (1779–1857), was a brickyard-owner, an architect, a Grand Duke council of Saxe-Weimar-Eisenach, who also worked as the construction manager in the reconstruction of the Wartburg. Alexander Saeltzer was born in Eisenach, Germany. He studied at Berlin Bauakademie and was a pupil of Schinkel's (presumably Karl Friedrich Schinkel). He moved to the U.S. from Berlin.
Saeltzer was engaged in February 1849 to design the synagogue at 172 Norfolk Street in an area of New York known as kleine Deutschland (Little Germany). The synagogue's Gothic Revival style was inspired by the Cologne Cathedral in Cologne, Germany, and Friedrichwerdesche Kirche in Berlin. According to a 1987 report by the New York City Landmarks Preservation Commission, while Gothic architecture is closely associated with Christianity, it had also become popular with synagogues as Jewish congregations had taken over old church buildings and become accustomed to the style, and viewed it as just as appropriate as any other architectural style.