Horst Ludwig Störmer (born April 6, 1949) is a German-born American Physicist, Nobel laureate and emeritus professor at Columbia University. He was awarded the 1998 Nobel Prize in Physics jointly with Daniel Tsui and Robert Laughlin "for their discovery of a new form of quantum fluid with fractionally charged excitations" (the fractional quantum Hall effect). He and Tsui were working at Bell Labs at the time of the experiment cited by the Nobel committee.

Störmer moved to France to carry out his PhD research in Grenoble, working in a high-magnetic field laboratory which was run jointly between the French CNRS and the German Max Planck Institute for Solid State Research. Störmer's academic advisor was Prof. Hans-Joachim Queisser, and he was awarded a PhD by the University of Stuttgart in 1977 for his thesis on investigations of electron hole droplets subject to high magnetic fields. He also met his wife, Dominique Parchet, while working in Grenoble.

Perhaps as important as the work for which he won the Nobel prize is his invention of modulation doping, a method for making extremely high mobility two dimensional electron systems in semiconductors. This enabled the later observation of the fractional quantum Hall effect, which was discovered by Störmer and Tsui in October 1981 in an experiment carried out in the Francis Bitter High Magnetic Field Lab at the Massachusetts Institute of Technology. Within a year of the experimental discovery, Robert Laughlin was able to explain its results. Störmer, Tsui and Laughlin were jointly awarded the 1998 Nobel Prize in Physics for their work.