On the Moon, Mars, or any location beyond Earth, where even the oxygen you breathe is made in a manufacturing process controlled by someone else, can you be free? Interplanetary Liberty: Building Free Societies in the Cosmos explores the conditions for freedom beyond Earth, proposing that space is especially prone to tyrannous coercive government. Rather than just accept this outcome, the book explores how political and economic arrangements, as well as facets of the legal system, science, engineering, art, and education in extraterrestrial settlements can be developed to encourage the emergence and persistence of free government in the cosmos. These efforts will maximise the chances of liberty taking hold beyond Earth, but they may be essential in the longer-term survival and development of human freedom anywhere in the cosmos, including Earth.