Eliezer Simon Kirschbaum (1797–1860) was an Austrian physician and writer.
After studying philosophy and medicine in Berlin, he settled as a physician in Kraków, and as "Der Berliner Doctor" soon acquired an extensive practice and accumulated a considerable fortune.
In order to be able to secure the estate of Siemota, near Chrzanów, he adopted the Christian religion, and assumed the name of "Sigismund."
As a married man he permitted his wife to remain a law-abiding Jew throughout her life.
Kirschbaum was the author of a long Hebrew essay, entitled "Hilkot Yeme ha-Mashiaḥ."