The Duke of Tresmes was a title in the peerage of France

Peerage of France

The Peerage of France was a distinction within the French nobility which appeared in the Middle Ages. It was abolished in 1789 during the French Revolution, but it reappeared in 1814 at the time of the Bourbon Restoration which followed the fall of the First French Empire...

 from 1648 to 1670, at which point the title was changed to Duke of Gesvres

Duke of Gesvres

The Duke of Gesvres was a title in the peerage of France from 1670 to 1794, named after Gesvres in northwestern France.-Background:...

. Thereafter, the Duke of Gesvres was sometimes referred to as the "Duke of Tresmes and Gesvres" and the title "Duke of Tresmes" was used as a courtesy title

Courtesy title

A courtesy title is a form of address in systems of nobility used for children, former wives and other close relatives of a peer. These styles are used 'by courtesy' in the sense that the relatives do not themselves hold substantive titles...

 for the eldest son of the Duke of Gesvres and "Count of Tresmes" for younger sons.

Background

The seigneury of Tresmes belonged to the Baillet family until the title fell to Charlotte Baillet, who married Louis Potier, Baron of Gesvres. Louis Potier succeeded in having the title raised to the title of Count of Tresmes (Fr. comte de Tresmes) in 1608. Their son René succeeded in having the title raised to Duke of Tresmes in 1648, and this title then passed to his son in 1669. The title was changed to "Duke of Gesvres" in 1670.

List

Individual	Title	From	To
René Baillet	Seigneur of Tresmes		1579
Louis Potier	Seigneur of Tresmes	1579	1608
	Count of Tresmes	1608	1630
René Potier	Count of Tresmes	1630	1648
	Duke of Tresmes	1648	1669
Léon Potier	Duke of Tresmes	1669	1670