Commodore Stone from TOS "The Court Martial"
|Played by Percy Rodriguez.|
What I think is amazing about Commodore Stone is that he was black and outranked Jim Kirk. "The Court Martial" originally aired in 1967, so having a white character being subordinate to a person of color was pretty damn bold for the time.
This episode was also notable for featuring an Indian or South Asian Starfleet captain named Chandra, but that's another post for another day.
Picture via Memory Alpha.