German botanist and lichenologist (1823-1884).
Ignaz Sigismund Poetsch (20 October 1823 – 23 April 1884) was a Bohemian-born physician and lichenologist in the Austrian Empire and later Austria-Hungary. Trained as a medical doctor in Prague and Vienna, he worked as a hospital physician in Vienna before spending most of his career as works doctor in Gaming and monastery physician in Kremsmünster, both in present-day Austria. Alongside his medical duties he developed an extensive expertise in cryptogamic botany, especially mosses and lichens, and became one of the main recorders of the lichen funga of Lower Austria, Upper Austria, and Styria