Johann Heinrich Casimir, Baron von Carmer (29 December 1720 in Kreuznach–23 May 1801 in Rützen, Silesia) was a Prussian judicial reformer.

He wrote in summary of the Miller's case, that the judiciary was: ...acting in self-interest, and [a judicial college] which practices injustices, is more dangerous and worse, such as a gang of thieves, [from which] one can protect oneself, but no one can guard against those who use the mantle of justice to carry out their evil passions.

He was relieved of his duties and a new Grand Chancellor, Maximilian von Fürst und Kupferberg [de] appointed; when he refused to arrest the recalcitrant judge from the original case, he also was dismissed by Frederick.

[2] Frederick realized that he needed to reshape the Prussian justice system, which was riddled with corruption, delay, and medieval punishments that were irrational and counterproductive.

[3] As Grand Chancellor, Carmer, Samuel von Cocceji, and another jurist, Carl Gottlieb Svarez, considered among the best legal minds of the age,[3] developed extensive reforms in Prussian justice, despite resistance in the Berlin judiciary circles.

Carmer not only wrote parts of these laws himself, but also provided the necessary support for the projects established by the King and for their defense against any entrenched judicial resistance.

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.