Georg Heinrich Gottlieb Jahr (French: Georges Henri Gottlieb Jahr; 30 January 1800 or 1801, Neudietendorf – 11 July 1875, Brussels) was a German-French physician. He was a pioneer of classical homeopathy. He published the first homeopathic repertory in 1835.
After studying in a Moravian college, about 1825 he got to know Samuel Hahnemann, whose assistant he became. On Hahnemann's recommendation, he went to the University of Bonn to get a medical education. After his graduation, he went to Liege to practice, but soon followed Hahnemann when the latter moved to Paris in 1835. He got his M.D. in Paris in 1840. He left Paris for Belgium on the outbreak of the Franco-Prussian War in 1870. In Belgium, he first went to Liege, then to Ghent, and finally to Brussels. Without a Belgian diploma, he was not allowed to practice medicine in Belgium, and this restricted his income.
Many of his numerous works have been published both in French and German, and translated into English by Charles Julius Hempel and others. Among them are treatises on the homeopathic treatment of cholera, of nervous and mental diseases, diseases of the skin, etc., and a Homœopathic Pharmacopœia.