Isaac de Razilly (1587 – December 1635) is a member of the French nobility appointed a knight of the Order of St. John of Jerusalem at the age of 18.

He was born at the Château d'Oiseaumelle in the Province of Touraine, France.

A member of the French navy, he serves for many years during which he plays an important role in the French colony of Acadia in New France.

He is the son of François de Razilly and Catherine de Valliers, brother of Claude de Razilly and François de Razilly.