Planetary chauvinism is the belief that human society will always be planet-based (even if extended beyond Earth), and overlooks or ignores the potential benefits of space-based living.^[1] The idea can be extended to alien society in general, that is, we should expect alien society to be planet based.^[2] The coining of the term is often credited to Isaac Asimov, but in an interview with Bill Boggs, Asimov mentions that he heard it from Carl Sagan.^[3] The counter-argument is that all the benefits of a planet can be achieved in space, usually by an O'Neill cylinder-type structure.^[4]

An even narrower version of planetary chauvinism is G-star chauvinism. This is the assumption that intelligent life will always evolve in star systems similar to our own, that is, in stars of spectral class G.^[5] Carl Sagan criticised this belief on the grounds that intelligent life has a greater chance of evolving on the most long lived stars. That suggests that class-M and class-K stars are more likely candidates, not only because of their lifetime, but also because they are far more numerous than class-G stars.^[2]