Samuel James Meltzer (March 22, 1851 – November 7, 1920) was an American physiologist, born in a village near Kaunas, then part of the Russian Empire.
Meltzer was educated at the University of Königsberg, studied philosophy and medicine at the University of Berlin (MD, 1882), and in the following year he emigrated to the United States, where he practiced his profession in New York City, serving as consulting physician to Harlem Hospital. In 1906 he became head of the department of physiology and pharmacology in the Rockefeller Institute for Medical Research. He served as president of the Harvey Society, of the Association for the Advancement of Clinical Research in 1909, and of the Association of American Physiologists in 1915. During World War I, Dr. Meltzer was a major in the Medical Reserve Corps, and when the American Association for Thoracic Surgery was organized in 1918 he was elected president. Dr. Meltzer was occupied in research in various fields almost to the time of his death.
Meltzer and his teacher Hugo Kronecker were the first who studied (in 1883) oesophageal manometry in humans.