(covers information from several alternate timelines)
Chief of staff was a title given to a senior member of a service organization or agency. This individual was usually responsible for overseeing the various branches of the service.
In 2293, General Chang was Chancellor Gorkon's chief of staff. (Star Trek VI: The Undiscovered Country)
In 2365, Elizabeth Vallis served as Prime Minister Wilson Granger's chief of staff at the Mariposa colony. (TNG: "Up The Long Ladder")
In 2366, Ki Mendrossen served as Ambassador Sarek's personal chief of staff. (TNG: "Sarek")
Starfleet chiefs of staff[]
The chief of staff had an office at Starfleet Command's Fleet Operations Center, San Francisco, Sol Sector. (ENT: "Demons", directories; VOY: "Non Sequitur", set artwork)
In 2372, Weyoun made a proposal to Captain Benjamin Sisko that the Dominion would make him absolute ruler of the Federation, with "no President or Starfleet chief of staff." (DS9: "To the Death")
In 2401, the dedication plaque of the USS Stargazer listed seven chiefs of staff. (PIC: "The Star Gazer")
The following individuals served as Starfleet chief of staff:
- E.W. Roddenberry – 2155
- Admiral Jonathan Archer – 2169
- R. Roddenberry – 23rd century
- R. Roddenberry – 23rd century, mirror universe
- T. Roth – 23rd century
- T. Roth – 23rd century, mirror universe
- Fleet Admiral Bob (last name unknown) – 2287
- Admiral Les Landau – 24th century
- Admiral Gene Roddenberry – 2363 – 2401
- Eugene Roddenberry (2401)
- Trevor Roth (2401)
- David Stapf (2401)
- Kevin Berg (2401)
- Jason Zimmerman (2401)
- Brian Tatosky (2401)