S'Sleen was a planet located somewhere in the space of the galaxy's Alpha or Beta Quadrants, in orbit of the Beta Virgilis star system, at coordinates 0.35S 2.08E. S'Sleen was of two inhabited planets orbiting Beta Virgilis, homeworld to the non-humanoid S'Sleen natives' civilization, the sister world to S'Sliss.
By the mid 23rd century, S'Sleen was under Prime Directive protection from the Federation. By reference stardate 2/2306.01 in the 2280s, the world had a population of around 1 billion individuals. (FASA RPG module: The Federation)