A Moff is an official in charge of a stellar sector.
Under the Star Imperium, a Moff was appointed by the Imperial Sovereign with the approval of the Imperial Parliament. The power to appoint sector Moffs passed to the Council of Twelve if the Sovereign was victim of incapacity or the position became vacant.
The title of Moff was also granted to the hereditary leaders of groups of families of Asguardian Dwarfs called clans. The hereditary Asguardian Dwarf nobles sitting in the Imperial Parliament officially used the title of Archon, though many of them used both titles.