Clermont-Tonnerre is the name of a French noble family, members of which played some part in the history of France, especially in Dauphiné, from about 1100 to the French Revolution (1789–99). Sibaud, lord of Clermont in Viennois, who first appears in 1080, was the founder of the family. His descendant, another Sibaud, commanded some troops which aided Pope Calixtus II in his struggle with the Antipope Gregory VIII. In return for this service, it is said that the pope allowed him to add certain emblems, two keys and a tiara to the arms of his family.