Emile Achard, full name Emile Charles Achard (24 July 1860 – 1944) was a French internist born in Paris.
In Paris, he served as médecin des hôpitaux (from 1893), later becoming a professor of general pathology and therapeutics. In 1910, he was appointed professor of internal medicine at the University of Paris. During his career, he also served as a physician at Hôpital Cochin.
In 1896, along with Raoul Bensaude (1866–1938), he identified a disease he called paratyphoid fever. They were able to isolate the cause of illness to a microbe now classified as salmonella paratyphi B.
A postmenopausal condition known as "diabetic-bearded woman syndrome" is now referred to as "Achard-Thiers syndrome", and the eponymous "Achard syndrome" is a disorder consisting of arachnodactyly, a receding lower jaw and joint laxity in the extremities.
In 1897, along with internist Joseph Castaigne (1871–1951), he 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.