Michel De Castelnai, sieur de la Mauvissiere, a French soldier and diplomatist, born at Mauvissiere about 1520, died at Joinville in 1592. lie entered the army in 1547, and won the favor of Francis of Lorraine, grand prior of France, under whom he afterward served in the navy, and who on becoming lieutenant general of the kingdom (1557) employed him in diplomatic missions to Scotland, England, Germany, the Netherlands, Savoy, and Koine. He negotiated a treaty with Queen Elizabeth, and dissuaded her from insisting on the restoration of Calais. In 15G0, after the death of Francis II., he accompanied Queen Mary to Scotland, and for a year rendered her efficient service in the field and in council. He distinguished himself in the civil war, negotiated a favorable treaty of peace with England, and was made governor of St. Dizier. He was again employed in various missions, was ambassador to England from 1574 to 1584, and on his return declared against the league. Henry IV. upon his accession treated him with great favor. His memoirs, written in England, extend over the period from 1559 to 1570, and are a valuable record of the events of the time.

They were published in 1621, and are to be found in Petitot's Alemoires relatifs a l'histoire de France. He translated the Latin work of Ramus on the ancient Gauls. His life, by Le Laboureur, was published in Paris in 1G59.