Fleet admiral
From Halopedia, the Halo wiki
File:Fleet Admiral Shoulder Board
This is the U.S. Navy Shoulder Board for a Fleet Admiral. The UNSC Navy uses the same insignia (stars), but the icon is likely that of the UNSC Navy.
Fleet Admiral is the highest commissioned officer rank of the UNSC Navy, and promotion to this rank is restricted to times of war.
As there is no equivalent in the UNSC Marine Corps, Fleet Admirals outrank all Marine Officers (as well as most Navy Officers).
Fleet Admirals typially lead battlegroups charged with the defence of key UNSC planets, such as Earth.
