Johannes Peter Müller (July 14, 1801, Koblenz - April 28, 1858, Berlin), was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.

In 1819 he entered Bonn University, where he became Privatdozent in 1824, extraordinary professor of physiology in 1826, and ordinary professor in 1830. In 1833 he removed to the university of Berlin, where he filled the chair of anatomy and physiology with great distinction until his death. Müller made numerous researches in various departments of physiology, and in particular he extended knowledge as to the mechanism of voice, speech and hearing, and as to the chemical and physical properties of lymph, chyle and blood.

The appearance of his Handbuch der Physiologie des Menschen between 1833 and 1840 (translated into English by Dr William Baly, and published in London in 1842) marked the beginning of a new period in the study of physiology. In it, for the first time, the results of human and comparative anatomy, as well as of chemistry and other departments of physical science, were brought to bear on the investigation of physiological problems.

The most important portion of the work was that dealing with nervous action and the mechanism of the senses. Here he stated the principle, not before recognized, that the kind of sensation following stimulation of a sensory nerve does not depend on the mode of stimulation but upon the nature of the sense-organ. Thus light, pressure, or mechanical stimulation acting on the retina and optic nerve invariably produces luminous impressions. This he termed the law of the specific energy of sense substances. In the later part of his life he chiefly devoted himself to comparative anatomy. Fishes and marine invertebrata were his favorite subjects. Müller numbered such distinguished scientists and physiologists as Hermann von Helmholtz, Emil du Bois-Reymond, Theodor Schwann, Jacob Henle and KFW Ludwig among his pupils.

In addition to his Handbuch der Physiologie, his publications include:

• Zur vergleichenden Physiologie des Gesichtssinns (1826)
• Uber die phantastischen Gesichtserscheinungen (1826)
• Bildungsgeschichte der Genitalien (1830), in which he traced the development of the Müllerian duct
• De glandularum secerneniium structura (1830)
• Vergleichende Anatomie der Myxinoiden (1834-1843)
• Systematische Beschreibung der Plagiostomen (1841) with FGJ Henle
• System der Asteriden (1842) with FH Troschel
• Horae ichthyologicae (1845-1849) with the same.

After the death of JF Meckel (1781-1833) he edited the Archiv fur Anatomie und Physiologie.