Ernst J. L. Gehrcke (1 July 1878 in Berlin – 25 January 1960 in Hohen-Neuendorf) was a German experimental physicist. He was director of the optical department at the Reich Physical and Technical Institute. Concurrently, he was a professor at the University of Berlin. He developed the Lummer–Gehrcke method in interferometry, he discovered anode rays, and he developed the multiplex interferometric spectroscope for precision resolution of spectral-line structures. As an anti-relativist, he was a speaker at an event organized in 1920 by the Working Society of German Scientists. He sat on the board of trustees of the Potsdam Astrophysical Observatory. After World War II, he worked at Carl Zeiss Jena, and he helped to develop and become the director of the Institute for Physiological Optics at the University of Jena. In 1949, he began work at the German Office for Materials and Product Testing. In 1953, he became the director of the optical department of the German Office for Weights and Measures.