Störmer, Horst Ludwig (1949-) is a German physicist who shared the 1998 Nobel Prize in physics with American physicist Daniel Chee Tsui and Robert B. Laughlin for their discovery of the fractional quantum Hall effect, which is a phenomenon in which electrons—the particles making up electric currents—divide into parts.

After receiving his Ph.D. degree in physics from Stuttgart University in 1977, Stormer began working for Bell Laboratories (now a part of Lucent Technology) in the United States, where he focused on semiconductors. There he worked with Tsui and in 1982, while conducting joint research on electrons, they observed a highly bizarre phenomenon. They found that when a semiconductor was subjected to temperatures near absolute zero and to extremely strong magnetic fields, its electrons behaved as though they had split into pieces with only a third of their normal charge, taking on the form of a type of quantum fluid. Prior to the discovery of this fractional quantum Hall effect, scientists had believed electrons to be the smallest elementary particles in existence, which would have made such fractional charges impossible. Thus, Stormer and Tsui's discovery indicated that particles smaller than electrons did exist. Laughlin later provided the theoretical explanation for the henomenon.

Laughlin and Stormer agreed the quantum Hall effect was unlikely to have immediate applications. However, Laughlin believes it has the potential to help in the understanding of the quantum structure of the vacuum throughout the space-time of the universe.

Stormer received the American Physical Society's Buckley Prize in 1984, the Otto Klung Physics Award in 1985, and the Benjamin Franklin Medal in Physics in 1998. He is on the faculty at Columbia University in New York City.