Sector Commander
Sector Commander (or CO, Sector) is responsible for coordinating all activity & responses within their specific sector. An example is Commodore Enwright, Who was the Commanding Officer of Starbase 6 in 2267 Reference: Star Trek TOS "The Ultimate Computer"
Sector Commanders can be of any Flag officer Rank, except that of Fleet Admiral which is reserved for the Commander-in-Chief of Starfleet.
In 2376, Rear Admiral Keisha Winters was made Commanding Officer - Sector of Sector 335 near the edge of the Beta Quadrant.