Starseeds, also called sailseeds, are a fictional life form in the Known Space science fiction series by Larry Niven. Fiction is the telling of stories which are not real More specifically fiction is an imaginative form of Narrative, one of the four basic Rhetorical modes. Known Space is the fictional setting of several Science fiction novels and short stories written by author Larry Niven. Laurence van Cott Niven (born April 30, 1938 Los Angeles California) is a US Science fiction author. These large (approximately one mile in diameter) "seeds" travel through interstellar space. Nothing is really known about them, other than they seem to migrate from the galactic center to the rim to eject their eggs, and then travel back to the core. The Galactic Center is the rotational center of the Milky Way Galaxy. Sometimes the eggs are ejected towards other galaxies, but most are left to hatch and migrate themselves to the core.

A starseed is typically spherical, but when it needs to change direction it unfolds itself into a large squarish solar sail with the four corners connected via strands to a small knob. Solar sails (also called light sails or photon sails, especially when they use Light sources other than the Sun) are a proposed form of Most of the internal organs are located in a cross-shaped swelling in the sail.

The aliens known as Outsiders follow starseeds for reasons only they know. The Outsiders are a fictional alien race in Larry Niven 's Known Space series Pierson's Puppeteers have once claimed to have a technology called "starseed lure" that can attract nearby starseeds to a specific solar system. They have supposedly used a starseed lure to influence the course of human/Kzin warfare by causing an Outsider ship to visit a human colony world, allowing humanity to purchase hyperdrive technology. The Kzinti (singular Kzin) are a Fictional, very warlike and bloodthirsty race of Cat-like aliens in Larry Niven 's Known Space series This technology allowed humanity to decimate the Kzinti in subsequent wars. However, other accounts have it that the outsiders followed an unmanned human starship that traveled between the human colonies (see A Gift From Earth). A Gift From Earth is a Science fiction novel by Larry Niven, first published in 1968 and set in his Known Space universe