The Fleet of Worlds are the home planets of the Pierson's Puppeteer race. They consist of the native homeworld, called "Hearth", and its agricultural worlds, arranged in a Klemperer rosette. The number of worlds has varied; at maximum (at the opening of the novel Fleet of Worlds) the Fleet comprised six worlds. By two Earth centuries later, in Niven's novel Ringworld, the Fleet contains five worlds.
The Puppeteers first moved their worlds into this formation when their home star turned into a red giant, using an inertialess, reactionless drive purchased at great price from the Outsiders. After the discovery that the core of the galaxy is exploding, the Puppeteers turned the fleet towards the Magellanic Clouds, gradually reaching a speed of 80% lightspeed. Although the Puppeteers have Faster-than-light technology they prefer to travel at safer, sub-light speeds.