Du Bellay, Guillaume (gēyōmˈ dü bĕlāˈ) [key], 1491–1543, French diplomat under King Francis I; brother of Jean Du Bellay. He was employed in negotiations regarding the Treaty of Cambrai (1529) between Francis and Holy Roman Emperor Charles V and in negotiations with King Henry VIII of England; he helped Henry secure French support for his divorce from Katharine of Aragón. He was also active in uniting German Protestant princes against Charles V and secured the Treaty of Scheyern (1532) with them. He served as governor of Turin (1537–39) and of the province of Piedmont (1539–42). He left an uncompleted manuscript history of the reign of Francis I.
See study by R. A. Katz (1985).