The megas doux (Greek: μέγας δούξ, pronounced [ˈmeɣaz ˈðuks], "grand duke") was one of the highest positions in the hierarchy of the later Byzantine Empire, denoting the commander-in-chief of the Byzantine navy. It is sometimes also given in English by the half-Latinizations megaduke or megadux. The Greek word δούξ is the Hellenized form of the Latin term dux, meaning leader or commander.