The setting is a distant future based on extrapolation of as much hard science as Niven had available. Specifically, it's the 29th century. "Known Space" (also the commonly used title for Larry Niven's future history science fiction series) is about 80 light years in diameter with 10,000 stars, including Human Space (40 light years diameter, 524 stars in 357 systems, 30 billion humans, ⅔ on Earth), as well as neighbouring Alien civilisations. Important Alien civilisations include the Puppeteers, paranoid pacifist herbivore centaurs, and the Kzinti, carnivorous warlike felines, who fought multiple wars over hundreds of years against the Humans, being defeated each time. Human allies include intelligent dolphins and orcas.