Star chart showing area where Diana was attacked
The Diana was a starship.
Sometime prior to 2364, the Diana was attacked. The location of this incident was marked in viewscreen readouts aboard the USS Enterprise-D on several occasions in 2364, in the form of star charts from the Enterprise-D library computer. (TNG: "The Naked Now", "The Last Outpost", "Conspiracy")
The Enterprise computer's star chart was a drawing by Rick Sternbach that had originally been published, years earlier, on page 95 of the reference titled Spaceflight Chronology. This chart showed early commercial lanes and exploration routes, but no text attesting to this fact was included in the portion used on screen, just the labeled names of the ship attack locations. The Diana was a commercial transport affiliated with the Federation, attacked with its cargo stolen and crew killed by Romulans prior to the Earth-Romulan War.