Huguenot cloth merchant whose execution caused the philosopher Voltaire to lead a campaign for religious toleration and reform of the French criminal code.

On Oct. 13, 1761, Calas's eldest son, MarcAntoine, was found hanged in his father's textile shop in Toulouse. Anti-Huguenot hysteria broke out among the local Roman Catholic populace, and Calas was arrested and charged with having murdered his son to prevent or punish his conversion to Catholicism. At first he attributed the crime to an unknown intruder, but he later insisted that his son had committed suicide. Found guilty by the local magistrates, he was condemned to death by the Parlement (appellate court) of Toulouse on March 9, 1762. The following day he was publicly broken on the wheel, strangled, and then burned to ashes. His son was buried as a martyr to the Catholic faith.

Influential friends of the family in Geneva interested Voltaire in the case, and through a vigorous press campaign the philosopher convinced large segments of European public opinion that Calas's judges had allowed their anti-Huguenot prejudices to influence their verdict. As a result, a 50-judge panel was appointed to review the case. The panel reversed Calas's conviction on March 9, 1765, and the government paid the family an indemnity. The Calas affair greatly strengthened the movement for criminal law reform and religious toleration in France, but the actual reforms were not instituted until the 1780s.