Sirius IX was the inhabited ninth planet in the Sirius system. This planet was located in the Beta Quadrant and was approximately 9 light years from Sol. The planet had at least a thousand inhabitants, who allegedly had a unique biochemistry.
At some point before stardate 4978, Harry Mudd sold a love potion to a thousand people on Sirius IX. When they became ill, Mudd quickly left the planet. (TAS: "Mudd's Passion"; TNG: "The Naked Now" production art)
Background information[]
This planet was only mentioned in dialogue.
This planet's quadrant of origin was inferred based on the position of its star system as seen in the star chart appearing in the Star Trek: The Next Generation episode "The Naked Now" and the position of certain stars and systems from that chart as seen in the star charts appearing in the Star Trek: Discovery episode "Magic to Make the Sanest Man Go Mad" and in the Star Trek: Picard episode "Maps and Legends".
In the Star Trek: Star Charts ("United Federation of Planets I"), Sirius IX listed as a Federation member in 2378.
The current location of Sirius IX in the Beta Quadrant was based on the most recent star charts seen in Star Trek: Strange New Worlds and Star Trek: Section 31.