Johann Heinrich Casimir, Baron von Carmer (29 December 1720 in Kreuznach–23 May 1801 in Rützen, Silesia) was a Prussian judicial reformer.
He was instrumental in the Miller Arnold case, which is an example of the principle of the independence of the judiciary.
He was instrumental in the creation of Corpus Juris Fridericianum for Frederick the Great, adopted into law in 1794.
For his achievements in the unification and modernization of Prussian law he was awarded the Black Eagle Order by King Frederick William II on 18 January 1788, and he was included among the names inscribed on the Equestrian statue of Frederick the Great in 1851.