Emile Achard, full name Emile Charles Achard (24 July 1860 – 1944) was a French internist born in Paris.
In 1893 he became médecin des hôpitaux, and later a professor of general pathology and therapeutics. In 1910 he was appointed professor of internal medicine at the University of Paris. He also was also a physician at Hôpital Cochin in Paris.
In 1896 with Raoul Bensaude (1866–1938), he identified a disease he called paratyphoid fever, and was able to isolate the cause to a microbe named salmonella paratyphi. Also a postmenopausal condition known as "diabetic-bearded woman syndrome" is now referred to as Achard-Thiers syndrome, and the eponymous Achard syndrome is a syndrome consisting of arachnodactyly, a receding lower jaw and joint laxity in the extremities.
In 1897 Achard and internist Joseph Castaigne (1871–1951) developed a urinary test using methylene blue dye to examine kidney function. The criteria used was to find the percentage of dye, injected subcutaneously, that showed up in the urine within a 24-hour period. This procedure was to become known as the Achard-Castaigne test. With Castaigne he published Manuel des maladies du tube digestif.