The title Duchess of Valentinois is the most concrete marker of where Diane de Poitiers stood in sixteenth-century France — a formal designation that names her among the French nobility at its highest reaches.

Born in Saint-Vallier, most likely in September 1499, though some sources place her birth in January 1500, Diane de Poitiers was a French noblewoman. She served as a lady-in-waiting, a position that situated her within the structures of court life, and she became in time a royal mistress. These three facts — noblewoman, lady-in-waiting, royal mistress — constitute what the record preserves of the shape of her life at court.

She held the title Duchess of Valentinois, and she lived and moved within France as a French-speaking noblewoman. The title itself is the clearest signal of the rank she occupied. Beyond the title and the roles named above, she was a citizen of France, female, and part of a court that conducted its affairs in the French language.

Diane de Poitiers died in 1566 at the Château d'Anet. That she died at the Château d'Anet in 1566, holding the title Duchess of Valentinois, is where the documented record of her life closes — a French noblewoman, born in Saint-Vallier near the end of the fifteenth century, who served as a lady-in-waiting and royal mistress, and who carried the title of duchess until her death.