Theta VIII, the location of the recreation of the Royale Hotel
The Theta 116 system was a star system that had remained unmapped by the United Federation of Planets until 2365, containing eight planets.
In 2365, the scattered remains of the 21st century Earth spaceship Charybdis were discovered in orbit of the farthest planet Theta VIII in this system by a Klingon cruiser. Subsequently the USS Enterprise-D entered orbit to investigate. (TNG: "The Royale")
Before "The Royale", two other Theta planets have been mentioned in Star Trek. Theta III seen on a star chart and Theta VII, a colony planet, where USS Enterprise delivered vaccines after the events in TOS: "Obsession" set in 2265. According to the FASA source book The Federation, the Theta VII colony was located in the Theta Gamma system.