Claude Casimir Gillet (19 May 1806 in Dormans, department of Marne – 1 September 1896 in Alençon), was a French botanist and mycologist. He initially trained as a medical doctor and veterinarian.
As a veterinarian, he worked for four years in Africa. Around 1853 he developed a passion for mycology, subsequently publishing a number of works on the subject. In 1867 he became a corresponding member of the Société Linnéenne de Normandie.